Chemistry 5070 · O Level · Experimental design

Experimental design — practice question

A student is recording how the temperature changes in the reaction of $\text{HCl\,(aq)}$ with aqueous sodium hydroxide, $\text{NaOH\,(aq)}$. $\text{NaOH\,(aq)} + \text{HCl\,(aq)} \rightarrow \text{NaCl\,(aq)} + \text{H}_2\text{O\,(l)}$
(a(i))[1]

State the reaction type for the process that occurs between $\text{HCl\,(aq)}$ and $\text{NaOH\,(aq)}$.

(a(ii))[1]

Name an item of apparatus that could make the volume of $\text{NaOH\,(aq)}$ added to the beaker more accurate.

(a(iii))[1]

Name the apparatus used to add the $4.0\ \text{cm}^3$ portions of $\text{HCl\,(aq)}$.

(a(iv))[2]

Explain why a glass beaker is not the best apparatus for this experiment. Suggest an improvement.

(a(v))[2]

Plot temperature against the total volume of $\text{HCl\,(aq)}$ on the grid.

(a(vi))[1]

Mark the anomalous point with a circle on the grid.

(a(vii))[1]

Draw a straight best-fit line through the points from $0$ to $16\ \text{cm}^3$.

(a(viii))[2]

Draw a straight best-fit line through the points from $20$ to $32\ \text{cm}^3$. Extend both lines until they meet.

(a(ix))[1]

Use the intersection to find the minimum volume of $\text{HCl\,(aq)}$ required to react with all of the $\text{NaOH\,(aq)}$.

(a(x))[1]

Use the intersection to work out the temperature change, $\Delta T$, caused by the reaction.

(a(xi))[1]

The heat change for this reaction is found from: heat change $=$ mass of solution $\times$ specific heat capacity $\times$ temperature change. $1.0\ \text{cm}^3$ of this solution has a mass of $1.0\ \text{g}$. State the value used for the mass of solution.

(b)[1]

The actual heat change for this reaction is much larger than the calculated value. Suggest one reason for this difference.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: Neutralisation / exothermic

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