x Turn on thread page Beta
 You are Here: Home

# Enthalpy change watch

1. The equation for the equilibrium between nitrogen and oxygen may be written intwo ways.

N2(g) + O2(g) <=> 2NO(g)
½N2(g) + ½O2(g) <=> NO(g)

The standard enthalpy change for the reaction as shown in the first equation is+180 kJ mol–1.

What is the standard enthalpy change for the reaction as shown in the secondequation?

A +45 kJ mol–1
B +90 kJ mol–1
C +180 kJ mol–1
D +360 kJ mol–1

I thought it was C as the answer is in the unit of per mole. But the correct answer is B.

2. (Original post by mystreet091234)
The equation for the equilibrium between nitrogen and oxygen may be written intwo ways.

N2(g) + O2(g) <=> 2NO(g)
½N2(g) + ½O2(g) <=> NO(g)

The standard enthalpy change for the reaction as shown in the first equation is+180 kJ mol–1.

What is the standard enthalpy change for the reaction as shown in the secondequation?

A +45 kJ mol–1
B +90 kJ mol–1
C +180 kJ mol–1
D +360 kJ mol–1

I thought it was C as the answer is in the unit of per mole. But the correct answer is B.

It's exactly what you just said. The enthalpy change is the energy released per mole.

If 180kJ is required to react 1 mole of N2 and 1 mole of O2 together,
then 90kJ is required to react 0.5 mole of N2 and 0.5 mole of O2 together

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: April 19, 2016
Today on TSR

### Loughborough better than Cambridge

Loughborough at number 1

### Can i date a girl with no boobs?

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