# Carbon dioxide output?

1. Aug 23, 2007

### mojo4king

Carbon dioxide output??

How would you go about calculating the carbon dioxide output per unit mass and volume for combustion products, i have already calculated the energy outputs per unit mass and volume.

Many thanks.

2. Aug 24, 2007

### Gokul43201

Staff Emeritus
Pick an example and show us what you would try.

3. Aug 24, 2007

### mojo4king

for eg. combustion of CH4:
CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(l)

enthalpy of combustion: (-393.51) + 2(-241.82) - (-74.81) = -802.34 kj/mol

energy output per unit mass:
802.34 x 1000/16(molar mass) = -50146.25 kj/kg

energy output per unit volume:
-50146.25 x 0.645(mass density) = -32344.33 kj/m3

However I have no clue on how to calculate the carbon dioxide output per unit mass and volume, any help would be kindly appreciated.
Many thanks.

4. Aug 24, 2007

### Gokul43201

Staff Emeritus
From the balanced equation, 1 mole of CH4 makes 1 mole of CO2. How much does a mole of CH4 weigh? What about a mole of CO2? And, at STP, what volume does a mole of (ideal) gas occupy.

5. Aug 24, 2007

### mojo4king

1 mole of CO2= 44g
1 mole of CH4= 16g
At STP the volume of an ideal gas occupies 0.0224 m3...

6. Aug 24, 2007

### mojo4king

for eg. combustion of CH4:
CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(l)

enthalpy of combustion: (-393.51) + 2(-241.82) - (-74.81) = -802.34 kj/mol

energy output per unit mass:
802.34 x 1000/16(molar mass) = -50146.25 kj/kg

energy output per unit volume:
-50146.25 x 0.645(mass density) = -32344.33 kj/m3

1 mole of CO2= 44g
1 mole of CH4= 16g
At STP the volume of an ideal gas occupies 0.0224 m3...

the CO2 energy output per mass....
-802.34 kj/mol divided by 12 g/mol equals 66.86 kj/g

am i doing the right thing, and how would you calculate the CO2 output per unit volume?

Many thanks.

7. Aug 24, 2007

### mojo4king

-802.34 kj/mol divided by 12 g/mol equals 66.86 kj/g
CORRECTION: DIVIDED BY 16G/MOL

8. Aug 25, 2007

### Gokul43201

Staff Emeritus
So, the CO2 output (assuming stoichiometric conditions) is:
44g of CO2 per mole of CH4
OR
2.75g of CO2 per g of CH4
OR
1 liter of CO2 per liter of CH4...etc.

9. Aug 25, 2007

### mojo4king

however i need to work out the CO2 output per unit mass and volume,
the units would be kj/kg and kj/m3,correct?

the CO2 energy output per mass....
-802.34 kj/mol divided by 12 g/mol equals 66860 kj/kg

the CO2 energy output per unit volume:
66860 x 0.645 (CH4 mass density)= 43124.7 kj/m3

Have i done these calculations properly?
Thanks.