IB Chemistry SL 2.1.3 Limiting Reactant Questions

Use real SL exam questions to compare reactants, identify the limiting reagent and calculate theoretical product yield.

Exam points

Compare each reactant amount with the balanced-equation coefficients to identify the limiting reactant and any excess reagent.
Use the limiting reactant to determine theoretical product amount or yield and calculate the amount of excess reactant remaining.
Show the stoichiometric comparison before reporting the chemically possible product mass, volume or amount after the limiting reactant is consumed.

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Study 2.1.3—Limiting reactant conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[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})

[ 3 ]

(i)

Determine the limiting reactant, showing your calculations.

[ 2 ]

《 $n_{\mathrm{HCl}}=2.00 \mathrm{~mol} \mathrm{dm}^{-3} \times 0.2000 \mathrm{dm}^{3}$ 》 $=0.400 \mathrm{~mol}$

« $\frac{0.400}{4}=$ » 0.100 mol AND $\mathrm{MnO}_{2}$ is the limiting reactant

Marking guidance:

Accept other valid methods of determining the limiting reactant in M2.

(ii)

Determine the excess amount, in mol , of the other reactant.

[ 1 ]

« $0.0307 \mathrm{~mol} \times 4=0.123 \mathrm{~mol}$ »

« $0.400 \mathrm{~mol}-0.123 \mathrm{~mol}=$ » 0.277 «mol»

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IB Chemistry SL 2.1.3 Limiting Reactant Questions question 1

Question (a)

Question (i)

Question (ii)