Chemistry 5070 · O Level · Exothermic and endothermic reactions

Exothermic and endothermic reactions — practice question

A student is investigating how much heat is given out when ethanol burns. The diagram shows the apparatus the student uses.
(a(i))[2]

State every measurement the student makes to obtain these values.

(a(ii))[1]

Why is a metal beaker chosen instead of a glass beaker?

(a(iii))[2]

Suggest two reasons why the temperature rise of the water was lower than the theoretical value.

(a(iv))[2]

Suggest two ways, using $1.0\,\text{g}$ of ethanol and $200\,\text{cm}^3$ of water, in which the apparatus can be modified to produce a temperature rise of more than $20\,^{\circ}\text{C}$.

(b)[1]

Calculate the number of moles of ethanol in $1.0\,\text{g}$. The relative formula mass of ethanol, $\text{C}_2\text{H}_5\text{OH}$, is $46$.

(c(i))[1]

What evidence in the table shows that all the reactions are exothermic?

(c(ii))[2]

Plot the data in the table on the grid. Draw a straight line of best fit. Extend your line to the left-hand side of the grid.

(d)[1]

Use your graph to predict the temperature rise for methanol.

(e(i))[1]

Explain why it is not possible to obtain a temperature rise of $90\,^{\circ}\text{C}$.

(e(ii))[1]

Suggest one way the student can obtain a temperature rise of $90\,^{\circ}\text{C}$.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: mass of burner and contents at the beginning and end

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