Year 12s: what will be the first way you research your future options? >>

calculating quantities of reagents in a experiement

I'm a bit stuck on how to tackle this question..I'm basically doing my A2 chemistry coursework which is the preperation of N-phenyethanamide invloving a 2 step process using phenylammonium chloride and ethanoic anhydride and some other reagents....

right what i'm stuck on is calculating the amount of each substance needed...(the question exactly is: calculate a suitable scale to give 1g of product assuming 70% yield)

Could someone please explain to me how i'm supposed to bring about answering this....

any help would be appreciated and thanks in advance :smile:

Reply 1

Artemidoros.

It's quite easy, all you need is a balanced reactant-product chemical equation for process.

You can then calculate how much reactant you need to give an IDEAL yield of 1g. Since the process is 70% efficient you multiply this quantity by 100 and then divide it by 70.

Reply 2

IChem

You need 1g of product but you only have a 70% yield:

The first step is to calculate how much mass 100% of the yield would be

1/\frac{70}{100}=1.429g

Now that you have the mass of the ideal yield you can calculate the number of mols in the ideal yield:

(n=\frac{m}{M}) n=\frac{1.429}{135}=0.106mols

Then from writing a balanced equation, using stochiometry you can find the number of mols of each reactant necessary. Multiplying these values will give you the mass needed of each reactant.