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

Oil and fat-containing food items are flushed with nitrogen. Why?

A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

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

What do you understand by precipitation reaction? Explain with examples.

In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

Write one equation each for the decomposition reactions where energy is supplied in the form of heat, light or electricity.

Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

Why is respiration considered an exothermic reaction? Explain.

What is meant by exothermic and endothermic reaction? Give an example.

Write the balanced chemical equations for the following reactions:(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water(b) Zinc + Silver nitrate → Zinc nitrate + Silver(c) Aluminium + Copper chloride → Aluminium chloride + Copper(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride

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 + HCI

Translate the following statements into chemical equations and then balance them.(a) Hydrogen gas combines with nitrogen to form ammonia.(b) Hydrogen sulfide gas burns in the air to give water and sulfur dioxide.(c) Barium chloride reacts with aluminum sulphate to give aluminum chloride and a precipitate of barium sulphate.(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

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

What happens when dilute hydrochloric acid is added to iron filings? (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced.

Fe2O3 + 2Al → Al2O3 + 2Fe What type of reaction is given above? (a) Combination reaction (b) Double displacement reaction. (c) Decomposition reaction. (d) Displacement reaction

Which statement is false regarding the reaction given below? 2PbO(s) + C(s) —> 2Pb(s) + CO(g) (a) Lead is reducing. (b) Carbon dioxide is getting oxidised.(c) Carbon is getting oxidised.(d) Lead oxide is getting reduced.

Identify the substances that are oxidised and the substances which are reduced in the following reactions:

Give an example of a double displacement reaction other than the one given in Activity 1.10 (NCERT). (i) 4Na(s) + O2(g) — 2Na2O(s) (ii) CuO (s) + H2(g) — Cu (s) + H2O(l)

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Why is the amount of gas collected in one of the test tubes in text book Activity 1.7 (i.e., electrolysis of water) double of the amount collected in the other? Name this gas.

A solution of a substance ‘X’ is used for white washing.(a) Name the substance ‘X’ and write its formula.(b) Write the reaction of the substance ‘X’ named in (a) above with water.

Write a balanced chemical equation with state symbols for the following reactions:(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.(ii) Sodium hydroxide solution (in water) reacts with a hydrochloric acid solution(in water) to produce sodium chloride solution and water.

Write the balanced equation for the following chemical reactions :(i) Hydrogen + Chlorine → Hydrogen chloride(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride(iii) Sodium + Water → Sodium hydroxide + Hydrogen

Why should a magnesium ribbon be cleaned before burning in air?

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