C2 PLEASE HELP ON CALCULATING THE PERCENTAGE STUFF!!!1 :S

  • 0 votes

Please can you help me with how to answer questions like this one on this link http://store.aqa.org.uk/qual/gcse/qp-ms/AQA-CHY2H-W-QP-JAN09.PDF 

Question 8a) and 8b) please help!!!!!!!!!!

:D thanks my exam is tomorrow!! 

Posted Tue 24th May, 2011 @ 20:59 by Zoeeee

3 Answers

  • 1 vote

Basically you are trying to work out how much aspirin that could be made from 2.00 g of salicylic

acid. this means that you have to divide 180 by 138 and this will give you the amount for one gram but you need to calculate it for two grams so you multiply the answer by two. you should get 2.61 as your final answer

part B is about percentage yield. The question gives you the actual value and you have calculated the predicted/theoretical in part A. so divide 1.1 by 2.61 and then multiply it by 100 because it is a percentage. 

Good luck in your exam tomorrow 

Answered Tue 24th May, 2011 @ 21:20 by Abbas M.M
  • 0 votes

Thank you so much that is really helpful does that mean you always calculate it to 1 gram and then multiply by what it asks you depending on the question? Sounds like it :) Thank You:D

Answered Tue 24th May, 2011 @ 22:57 by Zoeeee
  • 0 votes

yes that is correct. But you MUST read the question and what it is asking you:)

did u have the exam today? how was it?

Answered Wed 25th May, 2011 @ 18:32 by Abbas M.M