Question

6.

Mg(s) + 2 HCl(aq) → MgCl₂(aq) + H₂(g)
The chemical equation shown above represents the reaction between Mg(s) and HCl(aq). When 12.15 g of
Mg(s) is added to 500.0 mL of 4.0 M HCl(aq), 95 kJ of heat is released. The experiment is repeated with
24.30 g of Mg(s) and 500.0 mL of 4.0 M HCl(aq). Which of the following gives the correct value for the
amount of heat released by the reaction?

Answer 1

The correct value for the amount of heat released by the reaction is -15.84 kJ when 12.15 g of Mg is used, and -31.56 kJ when 24.30 g of Mg is used.

Step-by-step explanation:

The given chemical equation represents the reaction between solid magnesium (Mg) and hydrochloric acid (HCl) solution. When 12.15 g of Mg is added to 500.0 mL of 4.0 M HCl, 95 kJ of heat is released. To find the amount of heat released when 24.30 g of Mg is added to the same volume and concentration of HCl, we can use the concept of stoichiometry and molar ratios.

First, we need to determine the moles of Mg in both cases. The molar mass of Mg is 24.305 g/mol. Using the given mass, we can calculate:

12.15 g Mg * (1 mol Mg / 24.305 g) = 0.5001 mol Mg

24.30 g Mg * (1 mol Mg / 24.305 g) = 0.9999 mol Mg

Next, we can use the stoichiometry of the balanced equation to relate the moles of Mg to the heat released:

0.5001 mol Mg * (-95 kJ / 3 mol H₂) = -15.84 kJ

0.9999 mol Mg * (-95 kJ / 3 mol H₂) = -31.56 kJ

Therefore, the correct value for the amount of heat released by the reaction is -15.84 kJ when 12.15 g of Mg is used, and -31.56 kJ when 24.30 g of Mg is used.