The test for unsaturated compounds
3 marks · NormalWhen 28 g of ethene () gas reacts completely with bromine () solution in an addition reaction, calculate the maximum mass of 1,2-dibromoethane () that can be formed.
Give your answer to the nearest whole number. (Relative atomic masses: H = 1, C = 12, Br = 80)
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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188 g (±1)
Also accept: 187 g; 189 g
Common mistakes: Incorrectly using atomic masses for Br instead of Br_2; Not rounding to the nearest gram
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Calculates moles of ethene correctly using mol.
M2 · 1 mark · Uses stoichiometry of 1:1 ratio between ethene and 1,2-dibromoethane.
A1 · 1 mark · Calculates the correct mass of as 188 g (accept 187-189 g if rounding error). (follow-through)
Worked solution
First, calculate the moles of ethene used:
From the equation, 1 mol of produces 1 mol of .
Next, calculate the Mr of :
So, mass of formed = moles Mr = g
Final answer: 188 g