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IB Chemistry HL 2.1.3 Limiting reactant Question Bank

Practise IB Chemistry HL 2.1.3 by applying limiting reactant to exam-style questions.

Syllabus
First assessment 2025
Course
Chemistry HL
Level
HL

Exam points

  • identify the relevant chemical structure, process or evidence
  • apply the correct chemical model or equation
  • evaluate the result using chemical reasoning and data

2.1.3—Limiting reactant question 1

[Maximum number: 2]

Phosphine (IUPAC name phosphane) is a hydride of phosphorus, with the formula PH3\mathrm{PH}_{3}.

Question (a)

(a)

2.478 g of white phosphorus was used to make phosphine according to the equation:

P4( s)+3OH−(aq)+3H2O(l)→PH3( g)+3H2PO2−(aq)\mathrm{P}_{4}(\mathrm{~s})+3 \mathrm{OH}^{-}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{PH}_{3}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{PO}_{2}^{-}(\mathrm{aq})
[ 2 ]

Question (i)

(i)

This phosphorus was reacted with 100.0 cm3100.0 \mathrm{~cm}^{3} of 5.00 moldm−35.00 \mathrm{~mol} \mathrm{dm}^{-3} aqueous sodium hydroxide. Deduce, showing your working, which was the limiting reagent.

[ 1 ]

Question (ii)

(ii)

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

[ 1 ]
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