Question

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

specific heat capacity of the solution is 4.18 J/g°C. The enthalpy of the reaction is -23.4
kJ. If 1950 J of heat are released by this reaction, how many grams of Mgco, were
dissolved?

Answer 1

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

Step-by-step 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 =
`(1mol)/(23.4kJ)* 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* 84.3g/mol=6.99g`

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