Chemistry 5070 · O Level · Acid–base titrations

Acid–base titrations — practice question

A student uses titration to determine the percentage by mass of water in oxalic acid crystals.
(a)[1]

Calculate the mass of oxalic acid crystals that were used in the experiment.

(b)[1]

Name the apparatus in which solution $H$ is to be made up to $500\,\text{cm}^3$.

(c(i))[1]

Name the apparatus used for transferring $25.0\,\text{cm}^3$ of $H$ into the conical flask.

(c(ii))[1]

What colour is the solution in the conical flask when $G$ has just become in excess?

(d)[4]

Use the diagrams to fill in the titration table and find the average volume of $G$.

(e)[1]

Calculate the number of moles of potassium manganate(VII) in the average volume of $G$ used in (d).

(f)[1]

Deduce the number of moles of oxalic acid crystals present in $25.0\,\text{cm}^3$ of $H$.

(g)[1]

Deduce the number of moles of oxalic acid crystals in $500\,\text{cm}^3$ of $H$.

(h)[1]

Use your answers to (a) and (g) to calculate the relative formula mass of oxalic acid crystals.

(i)[2]

Oxalic acid crystals consist of water and oxalic acid, $\text{H}_2\text{C}_2\text{O}_4$. Use your answer to (h) to calculate the percentage by mass of water in oxalic acid crystals.

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