x Turn on thread page Beta
 You are Here: Home

# Chemistry bond enthalpies watch

1. the question is:
calculate the C≡C bond enthalpy in the gas propyne using the bond enthalpy values in the table ( table gives all relevant bond enthalpies) and the enthalpy changes for the reactions below.
C (s) ----> C (g) ∆H=715 kJ/mol
CH3C≡CH (g) ∆fH=185 kJ/mol

Am i right in saying i need to write out the equation of the combustion of propyne, if so what is the equation of C (s) ----> C (g) needed for
2. (Original post by FinnManley)
the question is:
calculate the C≡C bond enthalpy in the gas propyne using the bond enthalpy values in the table ( table gives all relevant bond enthalpies) and the enthalpy changes for the reactions below.
C (s) ----> C (g) ∆H=715 kJ/mol
CH3C≡CH (g) ∆fH=185 kJ/mol

Am i right in saying i need to write out the equation of the combustion of propyne, if so what is the equation of C (s) ----> C (g) needed for
Bond enthalpies are only valid for gaseous components.
3. (Original post by charco)
Bond enthalpies are only valid for gaseous components.
yes but how is this equation relevant C (s) ----> C (g) if C3H4+4O2--> 3CO2+2H2O where does the carbon by itself come in
4. (Original post by FinnManley)
yes but how is this equation relevant C (s) ----> C (g) if C3H4+4O2--> 3CO2+2H2O where does the carbon by itself come in
You are told to use bond enthalpy values to work out the enthalpy change of the equation.

Bonds broken are endothermic and bonds formed are exothermic.

So to use the bond enthalpy for CO2 you need to consider this equation:

C(g) + 2O(g) --> O=C=O

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: February 7, 2018
Today on TSR

### I have imposter syndrome at Cambridge

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