class 10th chemistry ke pahle chapter ki exercise
Answers
Answer:
1. Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) → 2Pb(s) + CO2(g)
(a) Lead is getting reduced
(b) Carbon Dioxide is getting oxidised
(c) Carbon is getting oxidised
(d) Lead oxide is getting reduced
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all
Solution:
(i) (a) and (b)
Explanation: (a) because Oxygen is being removed and (b) because the removed oxygen from Lead is added to the elemental Carbon.
2. Fe2O3 + 2Al → Al2O3 + 2Fe
The above reaction is an example of a
Combination reaction.
Double displacement reaction.
Decomposition reaction.
Displacement reaction.
Solution:
Answer is 4. Displacement reaction.
Explanation: The Oxygen from the Ferrous oxide is getting displaced to the Aluminium metal to form Aluminium Oxide. In this reaction Aluminum is more reactive metal than Fe. Therefore Al will displace Fe from its oxide. This type of chemical reactions in which one of the elements displace another is called displacement reaction. Here less reactive metal is displaced by more reactive metal. Since one-time displacement is occurring, therefore, it is called a single displacement reaction.
3. What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
Hydrogen gas and Iron chloride are produced.
Chlorine gas and Iron hydroxide are produced.
No reaction takes place.
Iron salt and water are produced.
Solution:
Hydrogen gas and Iron chloride are produced.
Explanation: The Chlorine from Hydrogen chloride is displaced by the Iron fillings to undergo the following reaction.
2HCl + Fe → FeCl2 + H2
4. What is a balanced chemical equation? Why should a chemical equation be balanced?
Solution:
A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equation is necessary for the reaction should obey The Law of Conservation of energy. Balancing the chemical equation has no defined method and is purely a trial and error attempt.
5. Translate the following statements into chemical equations and balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give Aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and Hydrogen gas.
Solution:
(a) Unbalanced: H2 + N2 → NH3
Balanced: 3H2 + N2 → 2NH3
(b) Unbalanced: H2S + O2 → H2O + SO2
Balanced: 2H2S + 3O2 → 2H2O + 2SO2
(c) Unbalanced:
BaCl2 + Al2(SO4)3 → AlCl3 + BaSO4
Balanced: 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4
(d) Unbalanced: K + H2O → KOH + H2
Balanced: 2K + 2H2O → 2KOH + H2
6. Balance the following chemical equations.
(a) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
(b) NaOH + H2SO4 → Na2SO4 + H2O
(c) NaCl + AgNO3 → AgCl + NaNO3
(d) BaCl2 + H2SO4 → BaSO4 + HCl
Solution:
(a) 2HNO3 + 2Ca(OH)2 → 2Ca(NO3)2 + 2H2O
(b) 6NaOH + 3H2SO4 → H2SO4 + 6H2O
(c) NaCl + AgNO3 → AgCl + NaNO3
(d) BaCl2 + H2SO4 → BaSO4 + 2HCl
7. Write the balanced chemical equation for the following reactions.
Calcium hydroxide + Carbon dioxide —-> Calcium carbonate + Water
Zinc + Silver nitrate —-> Zinc nitrate + Silver
Aluminium + Copper chloride —-> Aluminium chloride + Copper
Barium chloride + Potassium sulphate —-> Barium sulphate + Potassium chloride
Solution:
2Ca(OH)2 + 2CO2 → 2CaCO3 + 2H2O
Zn + 2AgNO3 → Zn(NO3)2 + 2Ag
2Al + 3CuCl3 → 2AlCl3 + 3Cu
BaCl2 + K2SO4 → BaSO4 + 2KCl
8) Write a balanced chemical equation for the following and identify the type of reaction of each case
KBr + BaI2 → KI + BaBr2
ZnCO3 → ZnO + CO2
H2 + Cl → HCl
Mg + HCl → MgCl2 + H2
Solution:
2KBr + BaI2 → 2KI + BaBr2 (Double Displacement Reaction)
ZnCO3 → ZnO + CO2 (Decomposition Reaction)
H2 + Cl → 2HCl (Combination Reaction)
Mg + 2HCl → MgCl2 + H2 (Displacement Reaction)
9) What is meant by exothermic and endothermic reactions? Give examples.
Solution:
An endothermic reaction occurs when energy is absorbed from the surroundings in the form of heat.(Example: Photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction is one in which energy is released from the system into the surroundings. (Example: Explosions, concrete setting, nuclear fission and fusion).
10. Why is respiration considered to be an exothermic reaction?
Solution:
For the survival of life, we require energy. We obtain this energy from the food we eat. The food molecules, through the process of digestion, is broken down into a simpler molecule like glucose. These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide and water along with a certain amount of energy (Respiration process). Since the energy is in the form of heat (that maintains our body temperature) the respiration is considered to be an exothermic reaction. The reaction taking place is:
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
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