Chemistry 5070 · O Level · Acid–base titrations

Acid–base titrations — practice question

A student is given solution K, which is aqueous sodium hydroxide, NaOH, and the concentration of K is found by titration.
(a)[1]

Name one piece of apparatus that can measure $25.0\,\text{cm}^3$ accurately.

(b)[1]

Name apparatus A.

(c)[1]

Why is it incorrect to rinse the burette with distilled water just before filling it with M?

(d)[1]

At the end-point, what colour change does methyl orange show? The colour changes from [BLANK] to [BLANK].

(e)[4]

Use the diagrams to fill in the table. Tick the best titration results and then use them to calculate the average volume of M.

(f)[1]

M is $0.0500\,\text{mol dm}^{-3}$ sulfuric acid, $\text{H}_2\text{SO}_4$. Determine the number of moles of $\text{H}_2\text{SO}_4$ in the average volume of M used during the titration.

(g)[1]

Dilute sulfuric acid reacts with aqueous sodium hydroxide as shown. $\text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}$ Find the number of moles of NaOH in $25.0\,\text{cm}^3$ of L.

(h)[1]

Find the number of moles of NaOH present in $500\,\text{cm}^3$ of L.

(i)[1]

Find the number of moles of NaOH present in $25.0\,\text{cm}^3$ of K.

(j)[1]

Find the concentration of NaOH in K, and give the answer to three significant figures.

(k)[2]

State and explain whether the second student's titration volume of dilute sulfuric acid would be smaller, larger, or unchanged compared with the first student's volume.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: Pipette or burette

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