Chemistry 5070 · O Level · Acid–base titrations

Acid–base titrations — practice question

A liquid hydrocarbon is ignited in the apparatus shown.
(a)[2]

Describe a chemical test that can be used to show that the colourless liquid collected in the boiling tube is water.

(b)[1]

Suggest why the boiling tube is put into a beaker of ice.

(c)[1]

What happens to the limewater in the conical flask when carbon dioxide is bubbled through it?

(d(i))[4]

Use the information shown in the diagram to fill in the results table.

(d(ii))[1]

Calculate the number of moles of $\text{HCl}$ in the mean volume of $1.00\text{ mol dm}^{-3}$ $\text{HCl}$.

(d(iii))[1]

Use the equation and your answer to (ii) to work out the number of moles of sodium hydroxide, $\text{NaOH}$, in $25.0\text{ cm}^3$ of Q. $\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}$

(d(iv))[1]

Calculate the number of moles of $\text{NaOH}$ in $100\text{ cm}^3$ of Q.

(d(v))[1]

Calculate the number of moles of $\text{NaOH}$ in the original $100\text{ cm}^3$ of $2.00\text{ mol dm}^{-3}$ $\text{NaOH}$.

(d(vi))[1]

Use your answers to (iv) and (v) to determine the number of moles of $\text{NaOH}$ that reacted with the carbon dioxide made when the hydrocarbon was burnt.

(d(vii))[1]

Use the equation and your answer to (vi) to determine the number of moles of carbon dioxide produced by burning the hydrocarbon. $\text{CO}_2 + 2\text{NaOH} \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O}$

(d(viii))[1]

The mass of hydrocarbon burnt is $0.73\text{ g}$. The $M_r$ of the hydrocarbon is $86$. Calculate the number of moles of hydrocarbon burnt.

(d(ix))[1]

This hydrocarbon is an alkane. The general formula of alkanes is $C_nH_{2n+2}$. Use your answers to (vii) and (viii) to calculate the value of $n$ in this hydrocarbon.

Worked solution & mark scheme

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