# IMAT 2014 Q 44 Chemistry

Hi, I’m having trouble solving this one without a calculator. Is there a trick that I’m missing? Thank you!

Hi!
First write out the reaction formula Zn + Pb(NO3)2→ Pb + Zn(NO3)2

1.30/65 = 0.02. Thus 0.02 moles of zinc react.

0.02 moles of lead should be produced theoretically.

However, 3.31/207 = 0.016 moles of lead is produced in the experiment

The percentage yield is thus 0.016/0.02 = 80%
Hey, this is how i did it and this is the most simplified calculation i got.
If anyone has a quicker method please share

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Hey Im also used to calculate % yield with moles, but I think it’s also possible to calculate it with the mass obtained (actual yield) and the mass we are suppose to get (Theoretical yield). What do you think? Generally it saves a bit of time, but I’m not sure.
Here I’d do the same as you at the beggining:
1.30/65 = 0.02. → 0.02 moles of zinc
then we would expect 0.02 moles of Pb in grams so…
0.02 * Mr of Pb = 0.02* 207 = 4.14 (THEORETICAL)
So the formula of percentage yield is:
3.31 / 4.14 . This calculation is time-consuming, but if we round it to 3/4 (75%) and we keep in mind that the number is a bit higher than it you get the answer (80%)

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Hi!
Yup I also primarily use this method but since the calculation was bit easier with moles i posted that HAHA

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