What is the difference between the subsequent two reactions ?
(a) Mg + 2HCl ——–> MgCl2 + H2
(b) NaOH + HCl ——–> NaCl + H2O.
Answer :
(a) It is a single displacement reaction,
(b) it's a double displacement also called neutralization .
Which of the subsequent may be a combination reaction and which may be a displacement ?
(a) Cl2 + 2KI ——–> 2KCl + I2
(b) 2K + Cl2 ——–> 2KCl.
Answer :
(a) It is a displacement reaction,
(b) It is a combination reaction.
Identify the foremost reactive and least reactive metal : Al, K, Ca, Au.
Answer :
Most reactive metal : K (potassium) ; Least reactive metal : Au (gold).
Fill in the Blanks : - The addition of oxygen to a substance is called …………. whereas removal of oxygen is called …………. .
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oxidation, reduction
Fill in the blanks :- ………….. is burnt in air to form magnesium oxide.
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Magnesium
Fill in the blanks :- Complete the missing components/variables given as x and y in the following reactions:
(a) Pb (NO3)2 (aq) + 2KI (aq) → Pbl2 (x) + 2KNO3 (y)
(b) Cu (s) + 2AgNO3 (aq) → Cu (NO3)2 (aq) + x (s)
Answer :
(a) x → (s); y → (aq);
(b) x → 2Ag
Fill in the blanks :- Na2SO4 + BaCl2 → …………. + 2NaCl
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BaSO4
Fill in the blanks :- 2 FeSO4 → Fe2O3 + SO2 + ………….
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SO3
Fill in the blanks :- …………. is the process in which metals are eaten up gradually by the action of air, moisture or a chemical on their surface.
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Corrosion
Fill in the blanks :- Two antioxidants which are usually added to fat and oil containing foods to prevent rancidity, are …………., …………. .
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BHA & BHT
Fill in the blanks :- Reaction in which an element displaces another element from its compound is called …………. .
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displacement reaction
Fill in the blanks :- Reactions in which energy is given out are known as …………. .
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exothermic reactions
Fill in the blanks :- Precipitation reactions produce insoluble …………. .
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salts
Fill in the blanks :- The addition of hydrogen to a substance is called …………. whereas removal of hydrogen is called …………. .
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reduction, oxidation
Fill in the blanks :- Magnesium is able to displace copper from copper sulphate solution because magnesium is ………….. reactive than copper.
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more
Fill in the blanks :- The oxidation and reduction reaction are also called ………….. reactions.
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redox
Fill in the blanks :- ………….. can be retarded by storing foods away from light.
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Rancidity
Fill in the blanks :- In rusting of iron, reddish brown coating formed on iron is …………..
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Fe2O3
Fill in the blanks :- ………….. are added to foods containing fats and oil.
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Antioxidants
Oxidation is the gain of ………….. or loss of …………..
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Answer: oxygen, hydrogen
Fill in the blanks :- Any reaction that produces a ………….. is called a precipitation reaction.
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Precipitate
Fill in the blanks :- Zinc and lead are more reactive elements than …………..
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copper
Fill in the blanks :- Respiration is an ………….. reaction.
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exothermic
Why doesn't a wall immediately acquire a white colour when a coating of calcium hydroxide is applied on it?
Answer :
Slaked lime as such is not very white. When applied on the wall, CO2 gas present in air reacts with calcium hydroxide to form calcium carbonate. It is quite white and therefore, imparts white look to the wall.
Ca(OH)2 + CO2(g) ———> CaCO3(s) + H2O(l).
What is rust ?
Answer :
It is a brown mass referred to as hydrated oxide . Its formula is Fe2O3.xH2O.
Describe an activity to observe what happens when quick lime is added to water taken in a beaker. State two important observations and name the type of reaction taking place.
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Aim: To observe what happens when quicklime is added to water taken in a beaker.
Materials Required:- Quicklime (calcium oxide), water, beaker.
Procedure:
1. Take 5 g of calcium oxide in a beaker.
2. Add water to it slowly.
3. Touch the beaker.
4. Note down the observations.
Observation: Calcium oxide reacts with water
vigorously to form calcium hydroxide with the evolution of heat.
Chemical Reaction:
Conclusion: The reaction between CaO (Calcium oxide) and H2O is a combination reaction. It is an exothermic process because heat is evolved.
What is meant by skeltal type chemical equation? What does it represent? Using the equation for electrolytic decomposition of water, differentiate between a skeltal chemical equation and a balanced chemical equation.
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The equations in which gaseous are written in atomic form instead of molecular form and equation is not balanced, are called skeltal type equation. They represent gaseous elements formed in atomic state and equation is not balanced
(a) Write one example for each of decomposion reaction carried out with help of
(i) Electricity (ii) Heat (iii) Light
(b) Which of the following statements is correct and why copper can displace silver from silver nitrate and silver can displace copper from copper sulphate solution.
Answer :
(a) Explain two ways by which food industries prevent rancidity.
(b) Discuss the importance of decomposition reaction in metal industry with three points.
Answer :
(a) (i) Rancidity can be prevented by adding antioxidants to food containing
fat and oil, e.g. butylated hydroxy anisole is added to butter as antioxidant.
(ii) It can be prevented by packaging fat and oil containing foods in nitrogen gas.
(b) (i) Molten NaCl is electrolytically decomposed to form sodium metal.
(ii) Aluminium metal is obtained by electric decomposition of bauxite ore mixed with cryolite.
(iii) Carbonate ores are thermally decomposed to give metal oxide which on reduction give metal.
(a) Define a balanced chemical equation. Why should an equation be balanced?
(b) Write the balanced chemical equation for the following reaction:
(i) Phosphorus burns in presence of chlorine to form phosphorus penta chloride.
(ii) Burning of natural gas.
(iii) The process of respiration.
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Answer :
(a) Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical reaction.
(b)(i) P4 (s) + 10Cl2 (g) ———> 4PCl5 (S)
(i)CH4 (g) + 2O2 (g) ———> CO2 (g) + 2H2O(l) + heat energy
(iii) C6H12O6 (s) + 6O2 (g) + 6H2O ———> 6CO2 (aq) + 12H2O (l) + energy
For the given reaction, match column I with column II and mark the correct option from the codes given below.
Fe2O3 + xCO → yFe + xCO2
|
Column I |
Column II |
|
(a) Oxidising agent |
(p) 2 |
|
(b) Reducing agent |
(q) 3 |
|
(c) x |
(r) Fe2O3 |
|
(d) y |
(s) CO |
|
Column I |
Column II |
|
(a) Oxidising agent |
(r) Fe2O3 |
|
(b) Reducing agent |
(s) CO |
|
(c) x |
(q) 3 |
|
(d) y |
(p) 2 |
Answer :
|
Column I |
Column II |
|
(a) Oxidising agent |
(r) Fe2O3 |
|
(b) Reducing agent |
(s) CO |
|
(c) x |
(q) 3 |
|
(d) y |
(p) 2 |
Answer :
(a) → (q)
(b) → (r)
(c) → (p)
(d) → (s)
|
Symbols |
Meaning |
|
(a) → |
(p) Aqueous |
|
(b) (g) |
(q) Yield or gives |
|
(c) Δ |
(r) Heat |
|
(d) (aq) |
(s) Liberation of gas |
Answer :
|
Symbols |
Meaning |
|
(a) → |
(q) Yield or gives |
|
(b) (g) |
(s) Liberation of gas |
|
(c) Δ |
(r) Heat |
|
(d) (aq) |
(p) Aqueous |
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