Which of the following statements is/are true?

Here are the solutions to the questions from the image.

Question 43:
The addition of excess magnesium to $100 \text{ cm}^3$ of $1.0 \text{ mol dm}^{-3}$ $\text{CuSO}_4\text{(aq)}$ raised the temperature from $25^\circ\text{C}$ to $55^\circ\text{C}$. What is the enthalpy change for the reaction? ($\text{C} = 4.18 \text{ J g}^{-1} \text{ K}^{-1}$, density of solution $= 1.0 \text{ g cm}^{-3}$)

Step 1: Calculate the heat absorbed by the solution ($q$).
The mass of the solution ($m$)