Question

(a) State the various characteristics of chemical reactions.
(b) State one characteristic each of the chemical reaction which takes place when
(i) dilute hydrochloric acid is added to sodium carbonate
(ii) lemon juice is added gradually to potassium permanganate solution
(iii) dilute sulphuric acid is added to barium chloride solution
(iv) quicklime is treated with water
(v) wax is burned in the form of a candle

Answer 1

(a) Characteristics of chemical reactions:

• Change in colour.

The colour of the reactants and products differs.

• Change in physical state.

The products formed can be a precipitate or gas or bubble or other.

• Change in odour.

An odour is produced during formation of product.

• Change in temperature.

The reaction can be exothermic (heat released) or endothermic reaction (heat absorbed).

(b) Example of chemical reaction:

(i) $\bold{2 \mathrm{HCl}+\mathrm{Na}_{2} \mathrm{CO}_{3} \rightarrow \mathrm{H}_{2} \mathrm{CO}_{3}+2 \mathrm{NaCl}}$

• The carbonic acid formed is unstable. So, the final reaction is given below.
• $\bold{H_{2} C O_{3}+2 N a C l \rightarrow C O_{2}+H_{2} O+2 N a C l}$
• The characteristic of the above chemical reaction is evolution of carbon dioxide in the form of effervescence (Change in physical state) and it is a decomposition reaction (carbonic acid is decomposed to carbon dioxide and water).

(ii) $\bold{3 \mathrm{KMnO}_{4}+\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7} \rightarrow 3 \mathrm{HMnO}_{4}+\mathrm{K}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}}$

• In this reaction, the potassium permanganate (purple colour) reacts with citric acid (reducing agent) to form permanganic acid and potassium citrate. The products formed becomes colourless.
• The characteristic of the above chemical reaction is change in colour and it is an oxidation reaction.

(iii) $\bold{H_{2} S O_{4(a q)}+B a C l_{2(a q)} \rightarrow B a S O_{4(s)} \downarrow+2 H C l_{(a q)}}$

• In this reaction, the sulphuric acid reacts with barium chloride to form barium sulphate which is a precipitate and hydrochloric acid.
• The characteristic of the above chemical reaction is change in physical state.

(iv) $\bold{C a O_{(s)}+H_{2} O_{(l)} \rightarrow C a(O H)_{2(s)}}$

• The quicklime reacts with water to form calcium hydroxide. In this reaction, heat energy is released during formation of product.
• The characteristic of the above chemical reaction is change in temperature.

(v) $\bold{C_{25} H_{52}+38 O_{2} \rightarrow 25 C O_{2}+26 H_{2} O}$

• The wax decomposes to form carbon dioxide (evolved as gas) and water. This is combustion reaction as wax burns.
• The characteristic of the above chemical reaction is change in physical state.

You can get all the answers of Chapter 1 in the link below:

https://brainly.in/question/13848082

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Answer 2

Answer:(i) Carbon dioxide formation.

(ii) Colour change from purple to clourless.

(iii) Barium sulphate a white precipitate is formed.

(iv) Temperature change.

(v) State change from solid to liquid and gas.

Explanation: