MYTUTOR SUBJECT ANSWERS

1270 views

Aspirin C9H8O4 is made when salicylic acid C7H6O3 reacts with ethanoic anhydride C4H6O3 . The equation for this reaction is: C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH Calculate the maximum mass of aspirin that could be made from 100 g of salicylic acid.

A relevant equation is:

mass = moles x relative formula mass 

Also written:

m = n*Mr

This reaction is a 1:1 ratio of salicylic acid to aspirin, meaning 1 mole of salicylic acid makes a maximum of 1 mole of aspirin. We know this because in the equation the coefficients to C9H8Oand C7H6O3 are both 1. 

So let's find out the number of moles of salicylic acid there is in 100g.

Mr salicylic acid = 138 g mol-1 because:

It has 7 Carbon atoms at 12g mol-1 and 6 Hydrogen atoms at 1g mol-1 and 3 Oxygen atoms at 16g mol-1.

7*12 + 6*1 + 3*16 = 138g mol-1

m/Mr = 100/138 = 0.7246...mol of salicylic acid.

There will also be 0.7246... mol of aspirin.

The Mr of aspirin is 180g mol-1. This can be found from the same method used to find the Mr of salicylic acid.

mass of aspirin = n * Mr = 0.7246... * 180 = 130.435... g

This rounds to 130g to 3.s.f.

It is 3 significant figures because this is the lowest degree of accuracy we have used throughout the question.

NOTES

A common easy mistake is to round within the question, ie. rounding the number of moles created to 0.725 or worse to 0.72 or 0.7. This can cause errors later in the question. Avoid this error by using the exact values in your final calculation. So where we calculated the mass of aspirin with

mass = n * Mr, use n = 100/138 in your calculator as this is the exact value. 

Emma H. IB Chemistry tutor, GCSE Chemistry tutor, IB Physics tutor, G...

8 months ago

Answered by Emma, a GCSE Chemistry tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist

155 SUBJECT SPECIALISTS

£18 /hr

Ed W.

Degree: Medicine (Bachelors) - Edinburgh University

Subjects offered: Chemistry, Maths+ 3 more

Chemistry
Maths
Further Mathematics
Biology
-Medical School Preparation-

“Hi! I'm Ed and I'm currently studying Medicine at the University of Edinburgh. I tutor at GCSE and A Level forBiology, Chemistry and Maths, and at GCSE level forFurther Maths. These are subjects I'm very comfortable in and enjoy. With ...”

MyTutor guarantee

£18 /hr

Matthew H.

Degree: Physics (Masters) - Liverpool University

Subjects offered: Chemistry, Physics+ 3 more

Chemistry
Physics
Maths
History
-Personal Statements-

“About Me  I am studying physics at the University of Liverpool and am now in my second year having passed with a first in all my modules last year. I really love all things science and have a real drive to pass on what I know to other...”

£22 /hr

Nathan L.

Degree: Materials Science (Masters) - Oxford, St Edmund Hall University

Subjects offered: Chemistry, Physics+ 1 more

Chemistry
Physics
Maths

“About Me: I'm a first year Materials science undergraduate at The University of Oxford. I loved learning about science and maths at school and hope my tutorials make you feel the same.  Structure: The key concept about tutorials i...”

About the author

Emma H.

Currently unavailable: until 01/09/2016

Degree: Natural Sciences (Physics and Maths) (Masters) - Leeds University

Subjects offered: Chemistry, Physics+ 4 more

Chemistry
Physics
Maths
History
French
English Literature

“What do I teach? I am a Natural Sciences (Physics and Maths) Masters student at Leeds University, but I also studied Chemistry in my first year of my degree.  I have tutored all three of these subjects at GCSE and A-Level, and I used ...”

MyTutor guarantee

You may also like...

Posts by Emma

Aspirin C9H8O4 is made when salicylic acid C7H6O3 reacts with ethanoic anhydride C4H6O3 . The equation for this reaction is: C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH Calculate the maximum mass of aspirin that could be made from 100 g of salicylic acid.

Differentiate y = 2x^3 + 6x^2 + 4x + 3 with respect to x.

Explore the ways in which pride is used as a theme in Antigone. Consider the dramatic techniques used by Sophocles and show how his choices of language, structure and style shape the meaning.

Integrate 4x^3 + 6x^2 +4x + 3

Other GCSE Chemistry questions

What is the volume of carbon dioxide released at room temperature and pressure when 6.2 g of copper carbonate reacts with excess dilute sulfuric acid?

What four factors influence the rate of reaction?

So, what actually is a mole?

Explain which species is oxidised in this reaction: Br2 +2I– = 2Br– +I2

View GCSE Chemistry tutors

Cookies:

We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok