Q14 of 39 Page 1

State the kind of chemical reactions in the following examples: (2014)

(i) Digestion of food in stomach


(ii) Combustion of coal in air


(iii) Heating of limestone


(i) Digestion of food in stomach: During digestion, the complex food is broken into simpler form.

Therefore, it is a type of decomposition reaction.


(ii) Combustion of coal is air: During combustion the coal burns in air to form CO2, H2O along with the evolution of heat. Thus, it is a type of exothermic decomposition reaction.


(ii) Heating of limestone: When limestone is heated strongly, it breaks into CO2 and lime. Thus it is a type of thermal decomposition reaction.


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12

Mention the rules for writing a chemical equation illustrating with the help of example. (2013)

 13

Select (i) combination reaction (ii) decomposition reaction and (iii) displacement reaction from the following chemical equations: (2014)

(i) ZnCO3 (s) → ZnO (s) + CO2 (g)


(ii) Pb (s) + CuCl2 (aq) → PbCl2 (aq) + Cu (s)


(iii) NaBr (aq) + AgNO3 (aq) → AgBr (s) + NaNO3 (aq)


(iv) H2 (g) + Cl2 (g) → 2 HCl (g)


(v) Fe2O3 + 2Al → Al2O3 + 2Fe


(vi) 3H2 (g) + N2 (g) → 2NH3 (g)


(vii) CaCO3 (s) CaO (s) + CO2 (g)


 15

Write the balanced chemical equation for the following reaction: (2014)

(i) Phosphorus burns in chlorine to form phosphorus pentachloride.


(ii) Burning of natural gas.


(iii) The process of respiration.


 16

(a) A substance X, an oxide of a metal, is used extensively in the cement industry. This element is found in our bones also. One treatment with water it forms a solution which turns red litmus blue.

Identity X and also write the chemical reaction involved.


(b) Choose a metal from the following metals which reacts only with hot water: Sodium, magnesium, iron.


Mention the products formed during the reaction. (2014)