Question

Calculate the oxidation numbers of the underlined element in each formula: S in H₂ S₄ (2) 3.1.2 Cl in ClO− (2) Determine which one of the following reactions is a redox reaction and explain your answer.

i. HCl(aq)+NaOH(aq)→ NaCl(aq)+H₂ O(I)
ii. Mg(s)+HCl(aq)→MgCl₂ (aq)+H₂ (g)
iii. AgNO₃ (aq)+NaCl(aq)→ AgCl(s)+NaNO₃(aq)

Answer 1

In the formula H₂S₄, the oxidation number of sulfur (S) is +6. In the formula ClO−, the oxidation number of chlorine (Cl) is +1. The redox reaction among the given options is ii. Mg(s) + HCl(aq) → MgCl₂(aq) + H₂(g).

Step-by-step explanation:

In the formula H₂S₄, the oxidation number of sulfur (S) is +6. This is because hydrogen (H) has an oxidation number of +1, and the sum of all oxidation numbers in the compound must equal zero. So, 2(+1) + x + 4(-2) = 0, where x is the oxidation number of sulfur. Solving this equation gives x = +6.

In the formula ClO−, the oxidation number of chlorine (Cl) is +1. This is because oxygen (O) has an oxidation number of -2, and the sum of all oxidation numbers in the compound must equal the charge of the ion. So, x + (-2) = -1, where x is the oxidation number of chlorine. Solving this equation gives x = +1.

The redox reaction among the given options is ii. Mg(s) + HCl(aq) → MgCl₂(aq) + H₂(g). In this reaction, magnesium (Mg) is oxidized from 0 to +2 (its oxidation number increases) and chlorine (Cl) is reduced from 0 to -1 (its oxidation number decreases). Therefore, this reaction is a redox reaction.