Chapter 1 : Chemical reactions

Q. What is the difference between displacement and double displacement reactions? Write equations for these reactions?

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Q. Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction

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Q. What is a balanced chemical equation? Why should chemical equations be balanced?

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Q. Translate the following statements into chemical equations and then 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.

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Q. Why do we apply paint on iron articles?

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Q. Write the balanced chemical equations for the following reactions.

(a) Calcium hydroxide + Carbon dioxide

\to

Calcium carbonate + Water

(b) Zinc + Silver nitrate

\to

Zinc nitrate + Silver

\to

Aluminium chloride + Copper

(d) Barium chloride + Potassium sulphate

\to

Barium sulphate + Potassium chloride

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Q. What do you mean by a precipitation reaction? Explain by giving examples.

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Q. Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity

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Q. Balance the following chemical equations:

(a)

H N O_{3} + C a {(O H)}_{2} \to C a {(N O_{3})}_{2} + H_{2} O

(b)

N a O H + H_{2} S O_{4} \to {N a}_{2} S O_{4} + H_{2} O

(c)

N a C l + A g N O_{3} \to A g C l + N a N O_{3}

(d)

B a {C l}_{2} + H_{2} S O_{4} \to B a S O_{4} + H C l

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Q. Write the balanced chemical equation for the following and identify the type of reaction in each case:

(a) Potassium bromide(aq) + Barium iodide(aq)

\to

Potassium iodide(aq) + Barium bromide(s)

(b) Zinc carbonate(s)

\to

Zinc oxide(s) + Carbon dioxide(g)

\to

Hydrogen chloride(g)

(d) Magnesium(s) + Hydrochloric acid(aq)

\to

Magnesium chloride(aq) + Hydrogen(g)

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Q. What does one mean by exothermic and endothermic reactions? Give examples.

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Q. A shiny brown coloured element

^{'} X^{'}

on heating in air becomes black in colour. Name the element

^{'} X^{'}

and the black coloured compound formed.

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Q. Why is respiration considered an exothermic reaction? Explain.

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Q. Which of the statements about the reaction below are incorrect?

2 P b O (s) + C (s) \to 2 P b (s) + C O_{2} (g)

(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.

(a) and (b)
(a) and (c)
(a), (b) and (c)
All

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Q. What happens when dilute hydrochloric acid is added to iron fillings?

Hydrogen gas and iron chloride are produced
No reaction takes place
Chlorine gas and iron hydroxide are produced
Iron salt and water are produced

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