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CBSE Solutions for Class 10 English

GSEB std 10 science solution for Gujarati check Subject Chapters Wise::

Give two important uses of washing soda and baking soda.

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જવાબ :

Washing soda Baking soda
1. It is used as an electrolyte 1. It can be used to test the garden soil for acidity. If bubbles are developed then the soil Is too acidic
2. It can be used domestically as water softener for laundry. 2. If used on washing car then it will remove dead bug bodies without damaging the colour or the paint on the car.


Why do acids not show acidic behavior in the absence of water?

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જવાબ : The acidic behavior from acids is because of the presence of hydrogen ions. Hydrogen ions can only be produced in the presence of water and therefore water is definitely needed if acids are to show their acidic behavior.


what's a neutralisation? Give two examples.

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જવાબ : The reaction of the acid + base gives a product of salt + water, which is taken into account as neutralization .
Examples:
NaOH + HCl → NaCl + H2O
Mg(OH)2 + H2CO3 → MgCO3 + 2H2O


Plaster of Paris should be stored during a moisture-proof container, explain with reasons?

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જવાબ : Plaster of Paris should be stored in moisture-proof container because moisture can affect plaster of Paris by slowing down the setting of the plaster due to hydration. this may turn plaster useless.


A milkman adds a really bit of bicarbonate of soda to fresh milk. Answer the subsequent questions.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take an extended time to line as curd?

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જવાબ : (a) He shifted the pH of the fresh milk from 6 to slightly alkaline to stop milk from getting sour thanks to production of carboxylic acid .
(b) This milk takes while to line into curd because the carboxylic acid produced here first neutralises the pH then the pH is reduced to show milk to curd.


Fresh milk features a pH of 6. How does one think the pH will change because it turns into curd? Explain.

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જવાબ : Fresh milk is turned to curd thanks to production of carboxylic acid . carboxylic acid reduces the pH of the milk.


Two equal lengths of magnesium ribbons are taken in test tubes A and B. acid (HCl) is added to check tube A, while ethanoic acid (CH3COOH) is added to check tube B. Amount and concentration taken for both the acids are same. during which tube will the fizzing occur more vigorously and why?

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જવાબ : HCl may be a strong acid whereas acetic may be a weaker acid. Fizzing occurs thanks to the assembly of the hydrogen gas obtained due to reaction of the acid on the magnesium ribbon. Since HCl may be a very strong acid there's tons of liberation of hydrogen gas from tube A. therefore, more fizzing happen in tube A.


Which sorts of medicines is employed for treating indigestion?

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જવાબ : Indigestion is thanks to excess production of acid within the stomach. Medicines wont to treat indigestion is named as Antacid.


10 mL of an answer of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of an equivalent solution of NaOH, the quantity HCl solution (the same solution as before) required to neutralise it'll be?

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જવાબ : Since 10 ml of NaOH requires 8 mL of HCL, 20 ml of NaOH require 8 x 2 = 16mL of HCl Hence the solution id option d 16mL.


an answer reacts with crushed egg-shells to offer a gas that turns lime-water milky. the answer contains what ?

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જવાબ : Answer is HCl.
Egg shells contains carbonate , which on reaction with HCl liberates CO2 gas which turn lime water to milky.
CaCO3 + 2HCl → CaCl2 + H2O + CO2


When an answer turns red litmus blue, its pH is probably going to be?

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જવાબ : Answer is 10 because paper turns blue when reacts with basic solution (PH quite 7).


Under what soil condition, a farmer would treat the soil of his fields with quick lime (calcium oxide) or calcium hydroxide (calcium hydroxide) or chalk (calcium carbonate)?

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જવાબ : If the soil is acidic in nature (PH below 7) then such field should be treated with quick lime (calcium oxide) or calcium hydroxide (calcium hydroxide) or chalk (calcium carbonate).


Do Basic solution even have H+(aq) ions? If yes, then why are these basic solutions?

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જવાબ : Yes,Basic solutions has H+ ions, but hydroxide ions present in basic solution are more in basic solution. Hence Hydroxide ions turn solution to basic.


What consequence does the concentration of H+(aq) ions wear the character of the solution?

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જવાબ : proton concentration decides the character of the answer . If proton concentration increase then solution turn acidic and similarly if proton concentration decreases then solution turn basic.


What consequence does the concentration of H+(aq) ions wear the character of the solution?

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જવાબ : proton concentration decides the character of the answer . If proton concentration increase then solution turn acidic and similarly if proton concentration decreases then solution turn basic.


you've got two solutions, X and Y. The pH of solution X is 6 and pH of solution Y is 8. Which solution has more proton concentration? Which of this is often acidic and which one is basic?

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જવાબ : so as to seek out the proton concentration, we will use the rule that states, “The pH of any solution is inversely proportional to the proton concentration”. Therefore, it means the answer that features a lower pH number will have a better proton concentration. Hence, solution X will have a better proton concentration. additionally , solution Y are going to be basic and X are going to be acidic.


How the concentration of hydroxide ions (OH–) affected when excess base is dissolved during a solution of sodium hydroxide?

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જવાબ : When base is dissolved in caustic soda solution its hydroxide ions increase but it'll reach saturation at some point. After saturation hydroxyl ion concentration isn't affected even after adding base further.


How is the concentration of hydronium ions (H3O+) is affected when a solution of an acid is diluted?

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જવાબ : When acid is added to water there'll be a hard and fast amount of hydronium present within the fixed volume of solution. If we dilute the answer hydronium ion per volume of solution decrease, this in-turn decreases Hydronium concentration within the solution.


While diluting an acid, why is it mostly recommended that the acid should be added to water and not water to the acid?

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જવાબ : While diluting an acid, it's recommended that the acid should be added to water and not water to the acid because if water is added to concentrated acid, it release huge amount of warmth which can end in explosion and may cause acid burns o face, clothes and body parts. Hence it's safe to feature acid to water but not water to acid.


Why does dry HCl gas does not change the colour of the dry litmus paper?

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જવાબ : HCL doesn't give out Hydrogen ions, therefore HCL doesn't show any acidic behaviour and colour of the paper remain an equivalent on reacting with HCl gas.


Why does an solution of acid conduct electricity?

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જવાબ : Charged particles are liable for the conductance of electricity in an acid. These charged particles called as ions are the rationale behind conductance of electricity in acid.


A Metal compound X reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one among the compounds formed is salt .

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જવાબ : As metal compound released is salt the gas evolved here is CO2. Hence metal X should be Calcium Carbonate. Hence the reaction between carbonate and HCl is
CaCO3 (s) + 2HCl (Aq) → CaCl2( Aq) + CO2 (g) + H2O (l)


Which gas is usually formed when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

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જવાબ : When an acid reacts with any metal, salt and hydrogen gas are formed.
Metal + Acid → Salt + Hydrogen gas


Why should sour substances like curd aren't kept in brass and copper vessels?

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જવાબ : Curd and sour food substances contain acids; these acidic substances combine with metal. This reaction turns food to poison which damage people’s health


write down an equation to show the reaction between Plaster of Paris and water.

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જવાબ : The chemical equation for the reaction of Plaster of Paris and water is
CaSO4.1/2H2O + 3/2H2O → CaSO4.2H2O


What will happen when a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

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જવાબ : Heating sodium hydrocarbonate yields sodium carbonate and carbon dioxide gas is liberated in the process.


Write the sodium compound which is used for softening hard water.

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જવાબ : washing soda is that the compound which is employed for softening water .


Write the name the substance which on treatment with chlorine yields chlorinated lime

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જવાબ : Calcium hydroxide.


Write the common name of the compound CaOCl2?

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જવાબ : bleaching powder.


Fill in the blanks :-  Among HCl, H2SO4 and CH3COOH, …………. is a weak acid.

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જવાબ : CH3COOH


Fill in the blanks :-  Mixing an acid or base with water leads to decrease within the concentration of per unit volume.This process is called

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જવાબ : OH– ions/H3O+ ions, dilution


Fill in the blanks :-  The presence of …………. Ca in acids is liable for their acidic properties.

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જવાબ :  H+


Fill in the blanks :-  During indigestion the stomach produces an excessive amount of …………. and this causes pain and irritation.

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જવાબ : acid (HCl)


Fill in the blanks :-  Use of mild base like …………. on the bee-stung area gives relief.

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જવાબ : baking soda


Fill in the blanks :-  The salts of a robust acid and weak base are …………. with pH value …………. than 7.

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જવાબ : acidic, less


Fill in the blanks :-  …………. is one among the raw materials for the assembly of bicarbonate of soda .

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જવાબ : Sodium chloride


Fill in the blanks :-  …………. is the fixed number of water molecules chemically attached to every formula unit of a salt in its crystalline form.

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જવાબ : Water of crystallization


Fill in the blanks :-  saltpeter has pH value adequate to …………. .

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જવાબ : 7


Fill in the blanks :-  …………. are obtained when bleaching powder reacts with dilute sulphuric acid.

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જવાબ : CaSO4, Cl2, H2O


Fill in the blanks :-  The pH of basic solution is always …………. than 7.

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જવાબ : greater


Fill in the blanks :-  Acids turn …………. litmus solution into …………. .

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જવાબ : blue, red


Fill in the blanks :- The process of formation of salt and water when an acid reacts with a base is called ……………. Process.

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જવાબ : neutralization


Fill in the blanks :- Boric acid is a …………….

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જવાબ : monobasic acid


Fill in the blanks :- The color of methyl orange in basic medium is …………….

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જવાબ : yellow


Fill in the blanks :- ……………. Soda is a deliquescent solid.

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જવાબ : Caustic soda


Fill in the blanks :- Hardness of water can be removed by …………….

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જવાબ : washing soda


Fill in the blanks :- Bleaching powder can be made by reacting …………….

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જવાબ : slaked lime with chlorine


Fill in the blanks :- An example of double salt is …………….

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જવાબ : Mohr’s salt


Fill in the blanks :- Phenolphthalein is ……………. in a acidic solution.

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જવાબ : colourless


Fill in the blanks :- Plaster of Paris is obtained from …………….

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જવાબ : gypsum


Fill in the blanks :- When a solution turns red litmus blue, its pH is likely to be …………….

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જવાબ : greater than 7


What is meant by are strong and weak acids? In the following list of acids, separate strong acids from weak acids.Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.

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જવાબ : Strong acids are those acids which are completely ionised in aqueous solution. Weak acids are those which do not ionise completely in aqueous solution. Strong acid: HCl,  HNO3,H2SO4 Weak acid: Citric acid, acetic acid, formic acid.


 (a) Mention the pH range within which our body works. Explain how antacids
give relief from acidity. Write the name of one such antacid.
(b) Fresh milk has a pH of 6. How does the pH will change as it turns to curd? Explain your answer.
(c) A milkman adds a very small amount of baking soda to fresh milk. Why does this milk take a longer time to set as curd?
(d) Mention the nature of toothpastes. How do they prevent tooth decay?

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જવાબ : (a) Our stomach has pH equal to 2. Antacids neutralizes excess of acid in our body and gives relief from hyperacidity. Sodium hydrogencarbonate is one of such antacid.
(b) pH will decrease as it turns to curd because curd is acidic due to the presence of lactic acid.
(c) It takes longer time to set as curd as bacteria do not work well in presence of sodium hydrogencarbonate, i.e. fermentation will take place slowly.
(d) Toothpastes are basic in nature. They neutralize the acid formed in mouth which causes tooth decay.


You have been given three test tubes. one among them contains water and therefore the other two contain an acidic solution and a basic solution, respectively. If you're given only red paper , how will you identify the contents of every tube ?

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જવાબ : (i) Put the red paper altogether the test tubes, turn by turn. the answer which turns red litmus to blue are going to be a basic solution. The blue paper formed here can now be wont to test the acidic solution.
(ii) Put the blue paper obtained above within the remaining two test-tubes, turn-by-turn. the answer which turns the blue paper to red are going to be the acidic solution.
(iii) the answer which has no effect on any paper are going to be neutral and hence it'll be water .


An alkali is a crucial base used for the laboratory work. Name the bottom and state how it are often prepared from common salt? what's this process called?

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જવાબ : An important alkali commonly needed for laboratory work is caustic soda . It are often prepared from common salt by the method of electrolysis. this is often called chlor-alkali process.
Electrolysis of solution of common salt : When electricity is skilled an solution of sodium chloride commonly called brine, it decomposes into chloride and sodium. Sodium is collected at the cathode where it reacts with water to make caustic soda . Chlorine is made at the anode and is collected as a gas.

electrolysis of NaCl

Cathode:

sodium hydroxide

At Anode:

Chlorine

The overall reaction is

chlor-alkali process


What are acids? Name a number of their properties.

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જવાબ : Acids are those chemical which produce hydrogen ions in its solution for example: acid , vitriol , acid etc.
Properties of Acids are
(i) it's sour in taste.
(ii) It turns blue litmus into red.
(iii) It turns azo dye colour into red.
(iv) Acids has corrosive in nature.


what's meant by bases? Write their properties.

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જવાબ : Bases are those chemical which produce hydroxide ions (OH-) in its solution for example: caustic soda , lime , milk of magnesia etc.
Properties of Bases are
(i) Base has bitter in taste.
(ii) Base convert red litmus into blue.
(iii) Base convert azo dye colour into yellow.
(iv) Base convert the color of Phenolphthalein into pink.
(v) Base doesn't react with metal.
(vi) Base doesn't react with metal carbonate and metal hydroxide carbonate thanks to its basic nature.
(vii) Only alkali bases are good conductor of electricity.


Describe the preparation of litmus solution.

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જવાબ : Litmus solution may be a purple dye which is extracted from a plant lichen. This dye is employed an indicator to tests for acids and bases. When litmus solution is neither acidic nor basic, its colour is purple. Acids change the color of blue litmus to red. Bases changes the red colour to blue.


Describe the method of dissolving acids or bases in water.

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જવાબ : When we dilute an acid with water then addition of acid in water may be a correct way of dilution because when water is added into acid then chemical reaction happen and much of warmth begin from the tube . thanks to which it can harm us while acid is added to water then endo thermic reaction happen thanks to assumption of warmth in water.


What does one understand by the term, “Ph scale”? what's the important use of this in our daily lives?

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જવાબ :
pH scale may be a scale for measuring hydrogen ions concentration. pH range between 0 to 14 thus, pH may be a number which indicate the acidic or basic nature of an answer . The neutral value of pH is 7. a worth but 7 represent an acidic solution, while a worth of quite 7 represent the essential nature of the answer .
Importance of pH in our daily life:
(i) pH of soil within the backyard: Every plant requires a selected pH for healthy growth. The optimum pH required for growth of a plant are often known by finding the pH of the place where such plant grow.
(ii) pH of our digestive system: Our stomach produce HCL which helps within the digestion of food. When the stomach has produce an excessive amount of acid we feel pain and irrigation which are the indication of indigestion. To face this problem we take antacid which neutralize excess acid and convey relief.
(iii) pH changes as explanation for tooth decay: enamel is phosphate and is that the hardest substance within the body. It doesn't dissolve with water buts gets corrode at pH below 5.5. Bacteria present within the mouth produce acid by dehydration of food particle left within the mouth after eating and thus spoil the teeth.
(iv) Plants and animal are pH sensitive: Living organism can survive within the narrow range (7.0 to 7.8) of pH. When acid precipitation flows into the river its lower the pH value and make survival of aquatic life difficult.


Discuss about Baking soda

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જવાબ :
i)Chemical Name: Sodium: Bi carbonate
(ii) Chemical Formula: NaHCO3
(iii) Formation: NaCl + CO2 + H2O → NH4Cl + NaHCO3
(iv) Colour and state: it's a white crystalline solid.
(v) Action of air: it's stable in air.
(vi) Solubility in water: it's soluble in water the answer are going to be alkali.
NOTE: We use bicarbonate of soda in bakery or in kitchen because once we add bicarbonate of soda in any substance it makes the food fluffy. Their CO2 is liable for the fluffiness of food like in cake. In bakery leaven is employed rather than bicarbonate of soda because leaven contain mild acid like hydroxy acid .
(vii) Uses of Baking soda: it's utilized in kitchen.
It is also utilized in medicine as antacid.
It is utilized in soda acid extinguisher .


What sort of precautions are used while handling acids within the laboratory?

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જવાબ : All living things are very sensitive to acids and an excessive amount of acid can kill cells or stop proper working of cells. Concentrated acid are very dangerous and will never be handled without protection.
The following projection must be observed while handling acids.
(i) Never attempt to touch or taste acid which are utilized in the laboratory.
(ii) Never add water into concentrated acid otherwise bottle will break. Always add conc. Acid to water very slowly with continuous cooling under running water.
 


An oldster complained about acute pain within the stomach. Doctor gave him alittle antacid tablet and he got immediate relief. Explain what actually happened ?

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જવાબ : The oldster was affected by acute acidity. Antacid tablet contains sodium bicarbonate (NaHCO3). It reacts with the acid (HCl) formed due to acidity and neutralizes its effect. that's how the oldster got relief.


A doctor applied surgical bandages on the fractured bones. What changes are likely to occur ?

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જવાબ : Surgical bandages are made up of Plaster of Paris. When applied on the fractured bones after making them wet, it changes into a tough mass called Gypsum.

Previous Year Question Papers for CBSE Class 10 Science Chapter 2 Acids, Bases and Salts 9

The hard mass keeps the bones in proper position and therefore the gap is slowly filled due to calcification that's happening on the broken parts. This helps in uniting broken bones and that they change to one piece again.


Explain with reasons :
(i) hydroxy acid may be a component of leaven utilized in making cakes.
(ii) Gypsum, CaSO4.2H2O is employed within the manufacture of cement.

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જવાબ : (i) Role of hydroxy acid in leaven (mixture of hydroxy acid and sodium bicarbonate ) is to neutralise washing soda formed upon heating sodium hydrogen carbonate.

In case it's not done, cake are going to be bitter and washing soda also will have injurious side effects.
(ii) The role of gypsum (CaSO4.2H2O) within the manufacture of cement is to hamper the method of setting of cement.


State the property in each case :
(i) as an antacid.
(ii) as a constituent of leaven .

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જવાબ : (i) it's weakly alkaline in nature and neutralizes acid (HCl) formed within the stomach.
NaHCO3 + HCl ———-> NaCl + H2O + CO2
(ii) It evolves CO2 within the sort of bubbles when cake is formed by baking. As a result, the cake becomes porous also as fluffy.


Some Crystals of copper sulfate are heated during a tube for a few time.
(a) what's the color of copper sulfate crystals (i) before heating (ii) after heating ?
(b) what's the source of liquid droplets seen on the inner top of the tube during the heating process ?

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જવાબ : (a) Colour of crystals before heating : blue.
Colour of crystals after heating : white.
(b) The liquid droplets formed within the inner top of the tube during the heating process are of water. it's released from the crystals of copper sulfate during heating.


(a) an answer features a pH of seven . Explain under the subsequent situations that how you'd you :
(i) increase its pH
(ii) decrease its pH
(b) If an answer changes the color of the litmus from red to blue, what are you able to say about its pH ?
(c) What are you able to say about the pH of an answer that liberates CO2 from washing soda ?

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જવાબ : (a) the answer with pH 7 is neutral. Its pH are often increased by adding alittle amount of base like caustic soda . Basic solutions have pH quite 7. Similarly, pH are often decreased by adding bit of acid like acid . Acidic solutions have pH but 7.
(b) The change in colour of litmus from red to blue indicates that the answer is of basic nature with pH quite 7.
(c) CO2 are often liberated by reacting washing soda solution with acid like dilute acid . This shows that the answer is of acidic nature with pH but 7.


Explain with reasons why :
(i) Common salt becomes sticky during the season
(ii) blue copperas changes to white upon heating
(iii) If bottle filled with concentrated vitriol is left open within the atmosphere accidentally , the acid starts flowing out of the bottle of its own.

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જવાબ : (i) Common salt contains the impurity of magnesium chloride (MgCl2) which is of deliquescent nature. When exposed to atmosphere, it becomes moist. Therefore, common salt becomes sticky during the rainy reason.
(ii) blue copperas (CUSO4.5H2O) upon heating changes to anhydrous copper sulfate (CUSO4) which is white in colour.
(iii) Concentrated vitriol is very hygroscopic. It absorbs moisture from air and gets diluted. Since the quantity increases, the acid starts flowing out of the bottle.


Answer the subsequent
(a) Name the raw materials utilized in the manufacture of washing soda by Solvay process .
(b) How is sodium bicarbonate formed during Solvay process separated from a mix of NH4Cl and NaHCO3 ?
(c) How is washing soda obtained from sodium bicarbonate ?

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જવાબ : (a) The raw materials used are : NaCl, lime stone or CaCO3 and NH3.
(b) Sodium bicarbonate (NaHCO3) is sparingly soluble or less soluble in water and gets separated as a preciptate while NH4Cl remains in solution. The precipitate is removed by filtration.
(c) Sodium bicarbonate is converted to washing soda upon heating.


Answer the following

(a) What is the action of red litmus on

  1. dry ammonia gas
  2. solution of ammonia gas in water ?
(b) State the observations you would make on adding ammonium hydroxide to aqueous solution of

  1. ferrous sulphate
  2. aluminium chloride.
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જવાબ : (a)

  1. Red litmus has no action on dry ammonia gas because it does not release any hydroxyl ions (OH)
  2. When passed through water, ammonia (NH3) is converted to ammonium hydroxide (NH4OH). It dissociates to give hydroxyl ions (OH) and the solution is basic in nature. Red litmus acquires a blue colour.
(b)

  1. A green precipitate of ferrous hydroxide would be formed by double displacement reaction.
    Previous Year Question Papers for CBSE Class 10 Science Chapter 2 Acids, Bases and Salts 16
  2. A white precipitate of aluminium hydroxide will be formed by double displacement reaction.


Answer the following
(a) Why does an aqueous solution of an acid conduct electricity ?
(b) How does the concentration of hydrogen ions [H3O]+ change when the solution of an acid is diluted with water ?
(c) Which has a higher pH value ; a concentrated or dilute solution of hydrochloric acid ?
(d) What would you observe on adding dilute hydrochloric acid to

  1. sodium bicarbonate placed in a test tube ?
  2. zinc metal in a test tube ?
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જવાબ : (a) An aqueous solution of an acid conducts electricity because in water, an acid (e.g. HCl) dissociates to give ions. Since the current is carried by the movement of ions, an aqueous solution of acid conducts electricity.
(b) Upon dilution, more of acid dissociates into ions. Therefore, concentration of [H3O]+ ions increases upon dilution.
(c) Although more [H3O]+ ions are formed upon dilution, but the number of ions per unit volume decrease. Therefore, pH will increase upon dilution.
(d)

  1. Carbon dioxide gas would evolve accompanied by brisk effervescene.
    NaHCO3 (s) + HCl (aq) ———–> NaCl(aq) + CO2(g) + H2O(aq)
  2. Hydrogen gas would evolve accompanied by brisk effervescene.
    Zn(s) + 2HCl (aq) ———–> ZnCl2(ag) + H2(g)


Answer the following
(a) A gas is produced when cone. H2SO4 is added to solid sodium chloride taken in a test tube and the tube is heated. The gas coming out through the delivery tube is passed over a dry litmus paper and then over a moist litmus paper. What would you observe ? Explain your answer,
(b) Fresh milk has pH of 6. When it changes to curd (yogurt), will its pH value increase or decrease ? Why ?
(c) What will be the colour of blue litmus in a solution of sodium carbonate ?

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જવાબ : (a) Upon heating sodium chloride with cone. H2SO4, hydrogen chloride gas evolves.
NaCl(s) + H2SO4(aq) ———> NaHSO4 (aq) + HCl (g)
In the gaseous state, the acidic character is not shown because HCl does not release any H+ ions. In the presence of moisture (moist litmus paper), the gas changes to hydrochloric acid i.e., HCl(aq). The acid releases H+ ions and thus, shows acidic character. Therefore, moist blue litmus paper becomes red.
(b) When fresh milk changes to curd, the pH of the solution is likely to decrease. Actually, lactose present in milk gets converted to lactic acid when curd or yogurt is formed from milk. Therefore, the medium becomes more acidic and its pH decreases.
(c) The solution of sodium carbonate (Na2CO3) is of basic nature. Actually, the salt dissolves in water to produce NaOH (strong base) and H2CO3(weak acid). The blue litmus will not undergo any change in the basic medium. It will remain blue.
Previous Year Question Papers for CBSE Class 10 Science Chapter 2 Acids, Bases and Salts 18


When electricity is passed through a common salt solution, sodium hydroxide is produced along with the liberation two gases ‘X’ and ‘Y’. The gas ‘X’ burns with a pop sound whereas ‘Y’ is used for disinfecting drinking water.
(i) Identify X and Y.
(ii) Give the chemical equation for the reaction stated above.
(iii) State the reaction of Y with dry slaked lime.

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જવાબ : (i) The gas ‘X’ is H2 and gas ‘Y’ is Cl2
(ii) The chemical equation for the reaction is :
Previous Year Question Papers for CBSE Class 10 Science Chapter 2 Acids, Bases and Salts 19
(iii) Cl2 reacts with slaked lime to form bleaching powder.
Ca(OH)+ Cl2 ———–> CaOCl2 + H2O.


Answer the following
(i) What are strong acids and weak acids ? Give an example for each.
(ii) A dry pellet of a common base ‘B’ when kept in open absorbs moisture and turns sticky. The compound is also formed by Chloralkali process. Identify B. What type of reaction occurs when B is treated with dilute hydrochloric acid ? Write the chemical equation.

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જવાબ : (i) The strength of an acid is expressed in terms of its H+ ions releasing tendency in aqueous solution or in terms of its degree of dissociation
(α). Strong acids have large value of α (close to one) while weak acids have comparatively less value. For example, hydrochloric acid (HCl) is a strong acid while acetic acid (CH3COOH) is a weak acid.
(ii) The available information suggests that the base ‘B’ present in the pellet is sodium hydroxide (NaOH). It is of deliquescent nature. It absorbs moisture from atmosphere and becomes sticky. The base reacts with dilute hydrochloric acid to form salt and water. This reaction is known as neutralisation reaction.
NaOH (aq) + HCl(aq) ———–> NaCl (aq) + H2O(l)


Write the chemical name along with the  formula of common salt. List two main sources of common salt in nature. Write any three uses of common salt. How is it connected to our freedom struggle?

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જવાબ : Sodium chloride (NaCl) also called common salt or table salt is the most essential part of our diet. Chemically it is formed by the reaction between solutions of sodium hydroxide and hydrochloric acid. Sea water is the major source of sodium chloride where it is present in the dissolved form alongwith other soluble salts such as chlorides and sulphates of calcium and magnesium. It is separated by some suitable method. Deposits of the salt are found in different parts of the world and is known as rock salt. The formation of rock salt is due to the slow evaporation of sea water which takes ages. When pure, it is a white crystalline solid. However, it is often brown due to the presence of impurities.
• Sodium Chloride — Essential for Life
Sodium chloride is quite essential for life. Biologically, it has a number of functions to perform such as in muscle contraction, in conduction of nerve impulses in the nervous system and is also converted into hydrochloric acid in the stomach which helps in the digestion of food. When we sweat, there is loss of sodium chloride and some. Other salts alongwith water. This leads to muscle cramps. The loss has to be compensated suitably by giving certain salt preparations to the patients. These are called electrolytes Electral powder is a very popular electrolyte.
• Chemicals from Common Salt
Sodium chloride is also a very useful raw material for different chemicals. A few out of these are : hydrochloric acid (HCl), washing soda (Na2CO3-10H2O), baking soda (NaHCO3) etc. Upon electrolysis, a strong solution of the salt (brine), sodium hydroxide, chlorine and hydrogen are obtained.
Apart from these, it is used in leather industry for the leather tanning. In severe cold, rock salt is spread on icy roads to melt ice. It is also, a fertilizer for sugar beet.


Explain what happens when a concentrated solution of sodium chloride (brine) is electrolysed ? Name the process. Write the equation of the reaction involved. Write the names of the products obtained. Mention one use of each product.

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જવાબ : Sodium chloride (NaCl) also called common salt or table salt is the most essential part of our diet. Chemically it is formed by the reaction between solutions of sodium hydroxide and hydrochloric acid. Sea water is the major source of sodium chloride where it is present in the dissolved form alongwith other soluble salts such as chlorides and sulphates of calcium and magnesium. It is separated by some suitable method. Deposits of the salt are found in different parts of the world and is known as rock salt. The formation of rock salt is due to the slow evaporation of sea water which takes ages. When pure, it is a white crystalline solid. However, it is often brown due to the presence of impurities.
• Sodium Chloride — Essential for Life
Sodium chloride is quite essential for life. Biologically, it has a number of functions to perform such as in muscle contraction, in conduction of nerve impulses in the nervous system and is also converted into hydrochloric acid in the stomach which helps in the digestion of food. When we sweat, there is loss of sodium chloride and some. Other salts alongwith water. This leads to muscle cramps. The loss has to be compensated suitably by giving certain salt preparations to the patients. These are called electrolytes Electral powder is a very popular electrolyte.
• Chemicals from Common Salt
Sodium chloride is also a very useful raw material for different chemicals. A few out of these are : hydrochloric acid (HCl), washing soda (Na2CO3-10H2O), baking soda (NaHCO3) etc. Upon electrolysis, a strong solution of the salt (brine), sodium hydroxide, chlorine and hydrogen are obtained.
Apart from these, it is used in leather industry for the leather tanning. In severe cold, rock salt is spread on icy roads to melt ice. It is also, a fertilizer for sugar beet.


(a) Write down the chemical formula of hydrated copper sulphate and anhydrous copper sulphate. Giving an activity illustrate how these are inter convertible.

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જવાબ : (a)CuSO4.5H2O is hydrated copper sulphate. CuSO4 is anhydrous copper sulphate.
Aim: To show crystalline salts contain water of crystallization.
Material Required: CuSO4.5H2O (Blue vitriol), boiling tube, burner, cork,
delivery tube, test tube, clamp stand.
Procedure: 1.Take 2g of CuSO4.5H2O in a boiling tube fitted in a clamp stand.
2.Observe its colour. Fit it with cork and delivery tube bent at two right angles which dips into a test tube.
3.Heat crystals in boiling tube.
4.Observe vapours being condensed in test tube.
5.Cool the crystals and add few drops of water into it.
Observation:Water vapours get condensed in a test tube and colour
of blue crystals changes into white. On adding water to anhydrous copper sulphate it changes into blue again.
Chemical Reaction :
acids-bases-salts-chapter-wise-important-questions-class-10-science-3
Conclusion : Crystalline substances have water of crystallization which are lost on heating. When we add water inCuSO4till a saturated solution is formed. On cooling, it gets converted into CuSO4.5H2Ocrystals and it shows that both are inter convertible.
acids-bases-salts-chapter-wise-important-questions-class-10-science-4


We know that a white powder is added while baking breads and cakes to make them soft and fluffy. Write the name of the powder. Name its main ingredients. Explain the function of each ingredient. Write the chemical reaction taking place when the powder is heated during baking.

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જવાબ : Baking powder.
It consist of sodium hyrogencarbonate and tartaric acid.
Sodium hydrogencarbonate gives CO2 which makes cake soft and fluffy. Tartaric acid neutralizes the bitterness due to sodium carbonate produced.
acids-bases-salts-chapter-wise-important-questions-class-10-science-8


(i) Dry pellets of a base ‘X’ when kept open absorbs moisture and turns sticky. The compound is also formed by chlorine-alkali process. Write chemical name and formula of X. Describe chlorine-alkali process with balanced chemical equation. Name the type of reaction occurs when X is treated with dilute hydrochloric acid. Write the chemical equation. (ii) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

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જવાબ : (i) X is sodium hydroxide, NaOH.
When sodium chloride solution (brine solution) is electrolysed, sodium hydroxide solution is formed. H2 and Cl2 gases are liberated. This is chlor-alkali process.
acids-bases-salts-chapter-wise-important-questions-class-10-science-13
The above reaction is neutralization reaction.
(ii)It is because process is highly exothermic. If water is added to acid, bottle of acid will break.


(a) Name the acid and the base whose combination forms the common salt that you use in your food. Write its formula and chemical name of this salt. Name the source from where it is obtained.
(b) What is rock salt? Mention its colour and the reason due to which it has this colour.
(c) What happens when electricity is passed through brine? Write the chemical equation for it.

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જવાબ : (a) HCl is acid and NaOH is base whose combination forms the common salt. Its formula is NaCl (Sodium chloride). It is obtained from sea water.
(b) Rock salt is the common name for the mineral “halite”. Its chemical formula is NaCl.
It may be white or light blue or yellow depending upon impurities present in it.
acids-bases-salts-chapter-wise-important-questions-class-10-science-12


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Match the important chemicals given in Column (A) with the chemical formulae given in Column (B)

Column (A)

Column (B)

(a) Plaster of Paris

(i) Ca(OH)2

(b) Gypsum

(ii) CaSO4. ½ H2O

(c) Bleaching Powder

(iii)CaSO4.2H2O

(d) Slaked Lime

(iv) CaOCl2

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જવાબ :

Column (A)

Column (B)

(a) Plaster of Paris

(ii) CaSO4. ½ H2O

(b) Gypsum

(iii)CaSO4.2H2O

(c) Bleaching Powder

(iv) CaOCl2

(d) Slaked Lime

(i) Ca(OH)2

Match the acids given in Column (A) with their correct source given in Column (B)

Column (A)

Column (B)

(a) Lactic acid

(i) Tomato

(b) Acetic acid

(ii) Lemon

(c) Citric acid

(iii) Vinegar

(d) Oxalic acid

(iv) Curd

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જવાબ :

Column (A) Column (B)

(a) Lactic acid (iv) Curd

(b) Acetic acid (iii) Vinegar

(c) Citric acid (ii) Lemon

(d) Oxalic acid (i) Tomato

Gas released by chemical reaction of zinc and sodium hydroxide
 

Neutralisation

Reaction between acid and base
 

Antacid

A substance that changes red litmus to blue

Hydrogen
 

Medicine used during indigestion
 

 

Base

 

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જવાબ :

a. Hydrogen

b. Neutralisation

c. Base
d. Antacid

Match the following

A synthetic indicator

Nettle

 Substance formed by hydration of plaster of Paris
 

Acid

A herbaceous plant with stinging hairs
 

Phenolphthalein

. Solution with pH less than 7
 

Gypsum

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જવાબ :

  1. Phenolphthalein
  2. Gypsum
  3. Nettle
  4. Acid

Column I

Column II

(a) Mixed salts

(p) CaCO3 MgCO3

(b) Double salts

(q) NaKCO3

(c) Basic salts

(r) NaHSO4

(d) Acidic salts

(s) CH3COONa

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જવાબ :

Column I

Column II

(a) Mixed salts

(q) NaKCO3

(b) Double salts

(p) CaCO3 MgCO3

(c) Basic salts

(s) CH3COONa

(d) Acidic salts

(r) NaHSO4

Column I

Column II

(a) Baking soda

(p) NaCl

(b) Plaster of Paris

(q) NaHCO3

(c) Washing soda

(r) CaSO. 1/2 H2O.

(d) Common salt

(s) Na2CO3

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જવાબ :

Column I

Column II

(a) Baking soda

(q) NaHCO3

(b) Plaster of Paris

(r) CaSO. 1/2 H2O.

(c) Washing soda

(s) Na2CO3

(d) Common salt

(p) NaCl

Column I

Column II

(a) Sodium carbonate

(P) Fire-proofing material

(b) Plaster of Paris

(q) Use for faster cooking

(c) Bleaching powder

(r) Softening hard water

(d) Baking soda

(s) Textile industry

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જવાબ :

Column I

Column II

(a) Sodium carbonate

(r) Softening hard water

(b) Plaster of Paris

(P) Fire-proofing material

(c) Bleaching powder

(s) Textile industry

(d) Baking soda

(q) Use for faster cooking

Match the chemical substances given in Column (A) with their appropriate application given in Column (B).

Column I

Column II

(A) Bleaching powder

(i) Preparation of glass

(B) Baking soda

(ii) Production of H2 and Cl2

(C)Washing soda

(iii) Decolourisation

(D) Sodium chloride

(iv) Antacid

(a) A-(ii), B-(i), C-(iv), D-(iii)
(b) A-(iii), B-(ii), C-(iv), D-(i)
(c) A-(iii), B-(iv), C-(i), D-(ii)
(d) A-(ii), B-(iv), C-(i), D-(iii)

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જવાબ :

(c) A-(iii), B-(iv), C-(i), D-(ii)

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