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# percentage yield help watch

1. Hi guys,

I'm reviewing AS content and I don't get why sometimes when calculating the actual/theoretical yield you do (100/percentage) instead of (percentage/100) to times by the moles, if that makes sense!

e.g. 'Synthesis of compound D from 1,3-diaminobenzene. 1.73g of compound D prepared. Overall percentage yield of compound D was 40%, Mr of compound D = 346.0, calculate the mass of 1,3 - diaminobenzene needed for this synthesis'

Mr of
1,3 - diaminobenzene = 108

Compound D mol = 1.73 / 346 = 5 x 10^-3
1,3 - diaminobenzene mol = 5 x 10^-3 x (100/40) = 0.0125
mass = 0.0125 x 108 = 1.35g

thanks in advance, sorry if its straight forward I'm at a blank!
2. Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

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Updated: November 11, 2017
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