You are Here: Home

# Stuck With Exam Question! watch

1. Hello,

I cant understand all of the following question, mark scheme attached:

(c) Write an equation for the reaction of propanoyl chloride with water.
An excess of water is added to 1.48 g of propanoyl chloride. Aqueous sodium hydroxide
is then added from a burette to the resulting solution.
Calculate the volume of 0.42 mol dm–3 aqueous sodium hydroxide needed to react
exactly with the mixture formed. (5 marks)

M1 CH3CH2COCl + H2O → CH3CH2COOH + HCl
(penalise wrong alkyl group once at first error)

M2 Mr of CH3CH2COCl = 92.5
(if Mr wrong, penalise M2 only)

M3 moles of CH3CH2COCl = 1.48/92.5 = 0.016 1

M4 moles NaOH = 2 × 0.016 = 0.032 1
(allow for × 2 conseq to wrong no of moles)

M5 volume of NaOH = 0.032/0.42 = 0.0762 dm3 or 76.2 cm3
(if ×2 missed in M4 lose M5 also)

I can understand up to M3 however I cannot see why the moles of NaOH have been multiplied by 2... could someone please explain this to me?

2. Oh damn.. i just read the mark scheme working again and I can see how 2 'separate moles' of acid are formed in M1 hence the consequential NaOH x 2...

Sorry!... how do i delete this thread?

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 13, 2010
Today on TSR

### Top unis in Clearing

Tons of places at all these high-ranking unis

### Why do women like men in suits?

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE