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GSEB Solutions for ધોરણ ૧૦ English

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

When a solution turns red litmus blue, its pH is likely to be …………….

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જવાબ : greater than 7


Plaster of Paris is obtained from …………….

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જવાબ : gypsum


Phenolphthalein is ……………. in an acidic solution.

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જવાબ : colorless


An example of double salt is …………….

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જવાબ : Mohr’s salt


Bleaching powder can be made by reacting …………….

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જવાબ : slaked lime with chlorine


Hardness of water can be removed by …………….

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જવાબ : washing soda


…………….  Soda is a deliquescent solid.

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જવાબ : Caustic soda


The color of methyl orange in basic medium is …………….

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જવાબ : yellow


Boric acid is a …………….

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જવાબ : monobasic acid


The process of formation of salt and water when an acid reacts with a base is called ……………. process.

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જવાબ : neutralization


Acids turn …………. litmus solution into …………. .

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જવાબ : blue, red


The pH of basic solution is always …………. than 7.

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જવાબ : greater


…………. are obtained when bleaching powder reacts with dilute sulphuric acid.

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જવાબ : CaSO4, Cl2, H2O


Potassium nitrate has pH value equal to …………. .

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જવાબ : 7


…………. is the fixed number of water molecules chemically attached to each formula unit of a salt in its crystalline form.

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જવાબ : Water of crystallization


…………. is one of the raw materials for the production of baking soda.

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જવાબ : Sodium chloride


The salts of a strong acid and weak base are …………. with pH value …………. than 7.

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જવાબ : acidic, less


Use of mild base like …………. on the bee-stung area gives relief.

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જવાબ : baking soda


During indigestion the stomach produces too much …………. and this causes pain and irritation.

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જવાબ : acid (HCl)


The presence of …………. Ca in acids is responsible for their acidic properties.

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જવાબ : H+


Mixing an acid or base with water results in decrease in the concentration of per unit volume.
This process is called

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જવાબ : OH ions/H3O+ ions, dilution


Among HCl, H2SO4 and CH3COOH, …………. is a weak acid.

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જવાબ : CH3COOH


Write the common name of the compound CaOCl2?

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જવાબ : bleaching powder.


Write the name the substance which on treatment with chlorine yields bleaching powder.

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જવાબ : Calcium hydroxide.


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

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જવાબ : Sodium carbonate is the compound which is used for softening hard water.


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


Why should sour substances like curd are not 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.


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


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 of the compounds formed is calcium chloride.

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


Why does an aqueous solution of  acid conduct electricity?

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


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

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જવાબ : HCL does not give out Hydrogen ions, therefore HCL does not show any acidic behavior and color of the litmus paper remain the same on reacting with HCl gas.


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 is 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 heat which may result in explosion and can cause acid burns o face, clothes and body parts. Hence it is safe to add acid to water but not water to acid.


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 will be a fixed amount of hydronium present in the fixed volume of solution. If we dilute the solution hydronium ion per volume of solution decrease, this in-turn decreases Hydronium concentration in the solution.


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

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જવાબ : When base is dissolved in sodium hydroxide solution its hydroxide ions increase but it will reach saturation at some point. After saturation point hydroxide ion concentration is not affected even after adding base further.


You have two solutions, X and Y. The pH of solution X is 6 and pH of solution Y is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?

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જવાબ : In order to find the hydrogen ion concentration, we can use the rule that states, “The pH of any solution is inversely proportional to the hydrogen ion concentration”. Therefore, it means that the solution that has a lower pH number will have a higher hydrogen ion concentration. Hence, solution X will have a higher hydrogen ion concentration. In addition, solution Y will be basic and X will be acidic.


What consequence does the concentration of H+(aq) ions have on the nature of the solution?

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જવાબ : Hydrogen ion concentration decides the nature of the solution. If Hydrogen ion concentration increase then solution turns acidic and similarly if Hydrogen ion concentration decreases then solution turn basic.


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

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


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


When a solution turns red litmus blue, its pH is likely to be?

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


A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains what ?

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


10 mL of a solution of NaOH is found to be completely neutralized by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralize it will 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 answer id option d 16mL.


Which types of medicines is used for treating indigestion?

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જવાબ : Indigestion is due to excess production of acid in the stomach. Medicines used to treat indigestion are called as Antacid.


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

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જવાબ : HCl is a strong acid whereas acetic is a weaker acid. Fizzing occurs because of the production of the hydrogen gas obtained due to reaction of the acid on the magnesium ribbon. Since HCl is a very strong acid there is a lot of liberation of hydrogen gas from test tube A. therefore, more fizzing take place in test tube A.


Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain.

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જવાબ : Fresh milk is turned to curd due to production of lactic acid. Lactic acid reduces the pH of the milk.


A milkman adds a very small amount of baking soda to fresh milk. Answer the following questions.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long time to set as curd?

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જવાબ : (a) He shifted the pH of the fresh milk from 6 to slightly alkaline to prevent milk from getting sour due to production of lactic acid. (b) This milk takes long time to set into curd because the lactic acid produced here first neutralizes the pH then the pH is reduced to turn milk to curd.


Plaster of Paris should be stored in 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 because of hydration. This will turn plaster useless.


What is a neutralization? Give two examples.

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


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 color or the paint on the car.


Why distilled water not conduct electricity, whereas rain water does?

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જવાબ :

  • Distilled water does not contain any ionic compounds in it.
  • Whereas rainwater has a lot, more compounds.
  • Rainwater has dissolved acidic gas such as carbon dioxide from the air and that forms carbonic acid. This means that it has hydrogen ions and carbonate ions. Therefore, with the presence of acids, rainwater can conduct electricity.


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.


You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?

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જવાબ : (i) Put the red litmus paper in all the test tubes, turn by turn. The solution which turns red litmus to blue will be a basic solution. The blue litmus paper formed here can now be used to test the acidic solution.
(ii) Put the blue litmus paper obtained above in the remaining two test-tubes, turn-by-turn. The solution which turns the blue litmus paper to red will be the acidic solution.
(iii) The solution which has no effect on any litmus paper will be neutral and hence it will be distilled water.


An alkali is an important base used for the laboratory work. Name the base and state how it can be prepared from common salt? What is this process called?

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જવાબ : An important alkali commonly needed for laboratory work is sodium hydroxide. It can be prepared from sodium chloride by the process of electrolysis. This is called chlor-alkali process.
Electrolysis of aqueous solution of sodium chloride: When electricity is passed through an aqueous 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 form sodium hydroxide. Chlorine is formed 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 some of their properties.

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જવાબ : Acids are those chemical which produce hydrogen ions in its aqueous solution for example: Citric acid, sulphuric acid, hydrochloric acid etc.
Properties of Acids are
(i) it is sour in taste.
(ii) It turns blue litmus into red.
(iii) It turns methyl orange color into red.
(iv) Acids are corrosive in nature.


What is meant by bases? Write their properties.

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જવાબ : Bases are those chemical which produce hydroxide ions (OH-) in its aqueous solution for example: Sodium hydroxide, Calcium hydroxide, Magnesium hydroxide etc.
Properties of Bases are
(i) Base have bitter taste.
(ii) Base convert red litmus into blue.
(iii) Base convert methyl orange color into yellow.
(iv) Base converts the color of Phenolphthalein into pink.
(v) Base does not react with metal.
(vi) Base does not react with metal carbonate and metal hydroxide carbonate due 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 is a purple dye which is extracted from plant lichen. This dye is used an indicator to tests for acids and bases. When litmus solution is neither acidic nor basic, its color is purple. Acids change the color of blue litmus to red. Bases change the red color to blue.


Describe the process 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 is a correct way of dilution because when water is added into acid then exothermic reaction takes place and lots of heat comes out from the test tube. Due to which it can harm us while acid is added to water then endo thermic reaction take place due to assumption of heat in water.


What do you understand by the term, “Ph scale”? What is the important use of this in our daily lives?

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જવાબ : pH scale is a scale for measuring hydrogen ions concentration. pH range between 0 to 14 thus, pH is a number which indicate the acidic or basic nature of a solution. The neutral value of pH is 7. A value less than 7 represent an acidic solution, while a value of more than 7 represent the basic nature of the solution.
Importance of pH in our daily life:
(i) pH of soil in the backyard: Every plant requires a specific pH for healthy growth. The optimum pH required for growth of a plant can be known by finding the pH of the place where such plant grow.

(ii) pH of our digestive system: Our stomach produces HCL which helps in the digestion of food. When the stomach has produced too much acid we feel pain and irrigation which are the indication of indigestion. To face this problem we take antacid which neutralize excess acid and bring relief.

(iii) pH changes as cause of tooth decay: Tooth enamel is calcium phosphate and is the hardest substance in the body. It does not dissolve with water buts gets corrode at pH below 5.5. Bacteria present in the mouth produce acid by dehydration of food particle left in the mouth after eating and thus spoil the teeth.

(iv) Plants and animal are pH sensitive: Living organism can survive in the narrow range (7.0 to 7.8) of pH. When acid rain flows into the river its lower the pH value and makes survival of aquatic life difficult.


Discuss about Baking soda.

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જવાબ : i) Chemical Name: Sodium: Bi carbonates
(ii) Chemical Formula: NaHCO3
(iii) Formation: NaCl + CO2 + H2O → NH4Cl + NaHCO3
(iv) Color and state: It is a white crystalline solid.
(v) Action of air: It is stable in air.
(vi)Solubility in water: It is soluble in water the solution will be alkali.
NOTE: We use baking soda in bakery or in kitchen because when we add baking soda in any substance it makes the food fluffy. Their carbon dioxide is responsible for the fluffiness of food like in cake. In bakery Baking powder is used instead of baking soda because baking powder contains mild acid like tartaric acid.
(vii) Uses of Baking soda: It is used in kitchen.
It is also used in medicine as antacid.
It is used in soda acid fire extinguisher.


What type of precautions is used while handling acids in the laboratory?

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જવાબ : All living things are very sensitive to acids and too much acid can kill cells or stop proper working of cells. Concentrated acid are very dangerous and should never be handled without protection.
The following projection must be observed while dealing with acids.
(i) Never try to touch or taste acid which are used 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 old person complained about acute pain in the stomach. Doctor gave him a small antacid tablet and he got immediate relief. Explain what actually happened?

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જવાબ : The old person was suffering from acute acidity. Antacid tablet contains sodium hydrogen carbonate (NaHCO3). It reacts with the acid (HCl) formed because of acidity and neutralizes its effect. That is how the old person 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 from Plaster of Paris. When applied on the fractured bones after making them wet, it changes into hard 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 the gap is slowly filled because of calcification that is taking place on the broken parts. This helps in uniting broken bones and they change to a single piece again.


(a) A solution has a pH of 7. Explain under the following situations that how you would you:
(i) increase its pH
(ii) decrease its pH
(b) If a solution changes the color of the litmus from red to blue, what can you say about its pH ?
(c) What can you say about the pH of a solution that liberates carbon dioxide from sodium carbonate?

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જવાબ : a) The solution with pH 7 is neutral. Its pH can be increased by adding a small amount of base like sodium hydroxide. Basic solutions have pH more than 7. Similarly, pH can be decreased by adding small amount of acid like hydrochloric acid. Acidic solutions have pH less than 7.
(b) The change in color of litmus from red to blue indicates that the solution is of basic nature with pH more than 7.
(c) Carbon dioxide can be liberated by reacting sodium carbonate solution with acid like dilute hydrochloric acid. This shows that the solution is of acidic nature with pH less than 7.


Explain with reasons why:
(i) Common salt becomes sticky during the rainy season
(ii) Blue vitriol changes to white upon heating
(iii) If bottle full of concentrated sulphuric acid is left open in the atmosphere by accident, 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 vitriol (CUSO4.5H2O) upon heating changes to anhydrous copper sulphate (CUSO4) which is white in color.
(iii) Concentrated sulphuric acid is highly hygroscopic. It absorbs moisture from air and gets diluted. Since the volume increases, the acid starts flowing out of the bottle.


Answer the following

(a) Name the raw materials used in the manufacture of sodium carbonate by Solvay process.
(b) How is sodium hydrogen carbonate formed during Solvay process separated from a mixture of NH4Cl and NaHCO3?
(c) How is sodium carbonate obtained from sodium hydrogen carbonate?

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જવાબ : (a) The raw materials used are: NaCl, lime stone or CaCO3 and NH3.
(b) Sodium hydrogen carbonate (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 hydrogen carbonate is converted to sodium carbonate upon heating.
Previous Year Question Papers for CBSE Class 10 Science Chapter 2 Acids, Bases and Salts 15


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. Aluminum 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 color.
(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 aluminum hydroxide will be formed by double displacement reaction.
    Previous Year Question Papers for CBSE Class 10 Science Chapter 2 Acids, Bases and Salts 17


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 effervescence.
    NaHCO3 (s) + HCl (aq) ———–> NaCl(aq) + CO2(g) + H2O(aq)
  2. Hydrogen gas would evolve accompanied by brisk effervescence.
    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 color 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 Chlor-alkali 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 neutralization 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 along with 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 are 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 along with 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. Electoral 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 electrolyzed ? 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 along with 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 are 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 along with 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 Electoral 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 color. 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 vapors being condensed in test tube.
5. Cool the crystals and add few drops of water into it.
Observation: Water vapors get condensed in a test tube and color
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 is 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


Answer the Following

 (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 neutralize excess of acid in our body and gives relief from hyperacidity. Sodium hyrogencarbonate 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 hyrogencarbonate, i.e. fermentation will take place slowly.
(d) Toothpastes are basic in nature. They neutralize the acid formed in mouth which causes tooth decay.


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


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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)

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

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

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) 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

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

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 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

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Acids, Bases, and Salts

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