Chemical Reactions and Equations Quiz

Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) → 2Pb(s) + CO2(g)

• Carbon dioxide is getting oxidised.

• Carbon is getting oxidised.

• Lead oxide is getting reduced.

• Lead is getting reduced.

Fe2O3 + 2Al → Al2O3 + 2Fe The above reaction is an example of a

• double displacement reaction.

• displacement reaction.

• combination reaction.

• decomposition reaction.

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.

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

• (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

• (c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

• (b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.

• (a) Hydrogen gas combines with nitrogen to form ammonia.

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 sulpur 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.

• (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.

• (b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.

• (a) Hydrogen gas combines with nitrogen to form ammonia.

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

• (a) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O

• (b) NaOH + H2SO4 → Na2SO4 + H2O

• (c) NaCl + AgNO3 → AgCl + NaNO3

• (d) BaCl2 + H2SO4 → BaSO4 + HCl

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

• (b) Zinc + Silver nitrate → Zinc nitrate + Silver

• (d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride

• (a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

• (c) Aluminium + Copper chloride → Aluminium chloride + Copper

Write the balanced chemical equation for the following and identify the type of reaction in each case. (a) Potassium br.

• (d) Potassium br.

• (c) Potassium br.

• (b) Potassium br.

• (a) Potassium br.

Recall Activity 1.1, where a magnesium ribbon burns with a dazzling flame in air (oxygen) and changes into a white substance, magnesium oxide. Is magnesium being oxidised or reduced in this reaction?

• Neither oxidised nor reduced

• Cannot be determined

• Reduced

• Oxidised

What you have learnt (a) A complete chemical equation represents the reactants, products and their physical states symbolically. (b) A chemical equation is balanced so that the numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation. Equations must always be balanced. (c) In a combination reaction two or more substances combine to form a new single substance. (d) Decomposition reactions are opposite to combination reactions. In a decomposition reaction, a single substance decomposes to give two or more substances. (e) Reactions in which heat is given out along with the products are called exothermic reactions. (f) Reactions in which energy is absorbed are known as endothermic reactions. (g) When an element displaces another element from its compound, a displacement reaction occurs. (h) Two different atoms or groups of atoms (ions) are exchanged in double displacement reactions. (i) Precipitation reactions produce insoluble salts. (j) Reactions also involve the gain or loss of oxygen or hydrogen by substances. Oxidation is the gain of oxygen or loss of hydrogen. Reduction is the loss of oxygen or gain of hydrogen.