Chemistry 5070 · O Level · Exothermic and endothermic reactions

Exothermic and endothermic reactions — practice question

When zinc is placed into aqueous iron(II) sulfate, the temperature of the mixture rises. $\text{Zn}(s) + \text{FeSO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{Fe}(s)$
(a(i))[1]

What can be inferred about the reaction from this information?

(a(ii))[1]

Why do the table temperatures fall from 1.0 to 6.0 minutes?

(a(iii))[1]

If temperature measurements had continued beyond 6.0 minutes, what lowest temperature would you expect to be reached?

(b(i))[3]

Plot the table data onto the grid. Then draw a straight line of best fit and continue it until it crosses the $y$-axis.

(b(ii))[1]

On the grid, circle the anomalous point.

(c(i))[1]

Use your graph to determine the mixture temperature at 2.5 minutes.

(c(ii))[1]

Use your graph to determine when the mixture temperature would be $30.0\,^{\circ}\text{C}$.

(d(i))[1]

Use your graph to determine the mixture temperature at 0.0 minutes. This value is the highest temperature reached during the reaction.

(d(ii))[1]

The starting temperature of the aqueous iron(II) sulfate was $22.0\,^{\circ}\text{C}$. Calculate the greatest temperature increase after zinc is added.

(e(i))[1]

Calculate the amount of substance, in moles, of iron(II) sulfate present in $25.0\,\text{cm}^3$ of $2.0\,\text{mol dm}^{-3}$ iron(II) sulfate.

(e(ii))[1]

The heat released in the reaction, in $\text{kJ mol}^{-1}$, is found from $\frac{25 \times 4.2 \times \text{maximum temperature rise}}{1000 \times \text{moles of iron(II) sulfate}}$. Apply this expression together with your answers to (d)(ii) and (e)(i) to determine the heat released in the reaction.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Exothermic

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI