IB Chemistry SL 1.4 Emission Spectra Question Bank

Practise IB Chemistry SL 1.4 with evidence-led questions on emission spectra, energy transitions and electron configurations.

Exam points

[Maximum number: 1]

How many ions are present in 0.20 mol of $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}$ ?

$0.20 \times 1 \times 6 \times 10^{23}$

$0.20 \times 2 \times 6 \times 10^{23}$

$0.20 \times 3 \times 6 \times 10^{23}$

$0.20 \times 7 \times 6 \times 10^{23}$

[Maximum number: 1]

The element boron has two naturally occurring isotopes, ${ }^{10} \mathrm{~B}$ and ${ }^{11} \mathrm{~B}$ .

The percentage abundance of the isotopes of boron can be determined with a mass spectrometer. The diagram shows the operation of a mass spectrometer.

Identify the species that is used as the scale for the mass of the isotopes.

[Maximum number: 3]

Chlorine undergoes many reactions.

(a)

2.67 g of manganese(IV) oxide was added to $200.0 \mathrm{~cm}^{3}$ of $2.00 \mathrm{moldm} \mathrm{m}^{-3} \mathrm{HCl}$ .

\mathrm{MnO}_{2}(\mathrm{~s})+4 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{MnCl}_{2}(\mathrm{aq})

[ 1 ]

(i)

Calculate the amount, in mol, of manganese(IV) oxide added.

[ 1 ]

n(\mathrm{MnO_2})=\frac{2.67\,\mathrm{g}}{86.94\,\mathrm{g\,mol^{-1}}}=0.0307\,\mathrm{mol}

(b)

$\mathrm{CCl}_{2} \mathrm{~F}_{2}$ is a common chlorofluorocarbon, CFC.

[ 2 ]

(i)

Calculate the percentage by mass of chlorine in $\mathrm{CCl}_{2} \mathrm{~F}_{2}$ .

[ 2 ]

$M(\mathrm{CCl_2F_2})=120.91\ \mathrm{g\ mol^{-1}}$ $\frac{2\times35.45}{120.91}\times100=58.64\%$

Award [2] for correct final answer.

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