Question

3) (Solid magnesium carbonate mixed in a solution of dilute hydrochloric acid. Assume the

Answer 1

Answer: The mass of magnesium carbonate that will be dissolved in the reaction is 6.99 g.

Explanation:

We are given:

Amount of heat released = 1950 J = 1.950 kJ                 (Conversion factor: 1 kJ = 1000 J)

The chemical equation for the reaction of magnesium carbonate and hydrochloric acid follows:

$MgCO_3+2HCl\rightarrow MgCl_2+H_2O+CO_2;\Delta H_{rxn}=-23.4kJ$

By Stoichiometry of the reaction:

If 23.4 kJ of heat is released, then 1 mole of magnesium carbonate is dissolved

So, when 1.950 kJ of heat is released, then = $\frac{1mol}{23.4kJ}\times 1.950kJ=0.083mol$ of magnesium carbonate is dissolved

To calculate the mass of the substance by given number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of magnesium carbonate = 0.083 moles

Molar mass of magnesium carbonate = 84.3 g/mol

Putting values in above equation, we get:

$0.083mol=\frac{\text{Mass of magnesium carbonate}}{84.3g/mol}\\\\\text{Mass of magnesium carbonate}=0.083mol\times 84.3g/mol=6.99g$

Hence, the mass of magnesium carbonate that will be dissolved in the reaction is 6.99 g.