Chem Multiple choice % yield Q!

(All 1:1 in formula)
In a preparation, with an excess of benzene, the mass of ethanoyl chloride (Mr = 78.5) used was 5.7 × 10−2 kg.
[1 mark]
The percentage yield of phenylethanone was 62%.
What mass, in grams, of phenylethanone was produced?
A 35g B 54g C 87g D 102g
[1 mark]
I got A buy apparently it’s B? Any help appreciated

Work out number of moles of ethanoyl chloride.
1:1 ratio
You got a number of moles of phenylethanone. Now use the Mr of phenylethanone to work out the maximum mass yield of it. I got around 87g.

Then you do 87 x 0.62 OR 87 x 62/100
Then you get 54g which is B

Edit: I suggest drawing the structure of phenylethanone if it was the Mr that got you.

Hi,

So are we expected to know the Mr of phenylethanone? (Or at least know how to work it out from the skeletal formula?)

You need to know how to work it out.
Given it is the product of the reaction described in the question (benzene + ethanoyl chloride, reacting in a 1:1 mole ratio and presumably in the presence of AlCl3), if you know your organic reactions, you should be able to work out the skeletal formula and hence it’s molecular formula and Mr.

Hi,

So are we expected to know the Mr of phenylethanone? (Or at least know how to work it out from the skeletal formula?)