Chemistry 5070 · O Level · The mole and the Avogadro constant

The mole and the Avogadro constant — practice question

A student is finding the mass of copper in mixture A, which contains only copper and zinc. Zinc reacts with dilute sulfuric acid, whereas copper does not. Dilute sulfuric acid is added to A in the apparatus shown below. A gas is produced and collected in B.
(a)[1]

Name the apparatus labelled B.

(b(i))[2]

Name the gas collected in B. Give a test and observation that can be used to identify the gas.

(b(ii))[1]

Construct an equation for the reaction of zinc with dilute sulfuric acid.

(c(i))[1]

Calculate the number of moles of gas in $96.0\,\text{cm}^3$. [At room temperature and pressure, $1$ mole of any gas occupies $24000\,\text{cm}^3$.]

(c(ii))[1]

Using your answers to (b)(ii) and (c)(i), calculate the mass of zinc present in A. [$A_r$: Zn, $65$]

(c(iii))[1]

The mass of mixture A is $1.20\,\text{g}$. Calculate the mass of copper present in mixture A.

(d)[1]

Once the reaction is complete, the student separates the copper from the solution left in the conical flask by filtration, using a filter paper that was weighed beforehand. Immediately after the filtration, the student weighs the filter paper with the copper residue and finds that its mass is larger than expected. Explain why.

Worked solution & mark scheme

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