A sample of natural gas is 80.0% CH4 and 20.0% C2H6 by mass. What is the heat from the combustion of 1.00 g of this mixture? Assume the products are CO2 and H2O.
How do I do this
You will need to know delta H for the combusion of CH4 and delta H for the combustion of C2H6. Then take 80% of 1 g for methane and 20% of 1 g for ethane and calculate delta H for each of the gases. Then add them together.
so CH4 = -74.87
and C2H6 = -84.68
what do you mean by take 80% and 20%???
To calculate the heat from the combustion of the given natural gas mixture, we need to determine the moles of CH4 and C2H6 in the sample first.
1. Calculate the mass of CH4:
Mass of CH4 = Percentage of CH4 × Total mass of the sample
Mass of CH4 = 80.0% × 1.00 g = 0.80 g
2. Calculate the mass of C2H6:
Mass of C2H6 = Percentage of C2H6 × Total mass of the sample
Mass of C2H6 = 20.0% × 1.00 g = 0.20 g
3. Determine the moles of CH4:
Moles of CH4 = Mass of CH4 / Molar mass of CH4
The molar mass of CH4 is 12.01 g/mol (carbon) + 4(1.01 g/mol) = 16.05 g/mol.
Moles of CH4 = 0.80 g / 16.05 g/mol
4. Determine the moles of C2H6:
Moles of C2H6 = Mass of C2H6 / Molar mass of C2H6
The molar mass of C2H6 is 2(12.01 g/mol) + 6(1.01 g/mol) = 30.07 g/mol.
Moles of C2H6 = 0.20 g / 30.07 g/mol
5. Balance the chemical equation for the combustion of CH4 and C2H6:
CH4 + 2O2 -> CO2 + 2H2O (balanced equation for combustion of methane)
C2H6 + 7/2O2 -> 2CO2 + 3H2O (balanced equation for combustion of ethane)
6. Calculate the moles of O2 consumed for the combustion of each compound:
Moles of O2 consumed for CH4 = Moles of CH4 × 2
Moles of O2 consumed for C2H6 = Moles of C2H6 × 7/2
7. Calculate the moles of CO2 and H2O formed for each compound:
Moles of CO2 from CH4 = Moles of CH4 × 1 (from the balanced equation)
Moles of H2O from CH4 = Moles of CH4 × 2 (from the balanced equation)
Moles of CO2 from C2H6 = Moles of C2H6 × 2 (from the balanced equation)
Moles of H2O from C2H6 = Moles of C2H6 × 3 (from the balanced equation)
8. Calculate the total heat released:
Heat released = (Moles of CO2 from CH4 × Heat of combustion of CO2) + (Moles of H2O from CH4 × Heat of combustion of H2O) + (Moles of CO2 from C2H6 × Heat of combustion of CO2) + (Moles of H2O from C2H6 × Heat of combustion of H2O)
The heat of combustion values for CO2 and H2O can be obtained from standard reference tables.
By following these steps, you should be able to calculate the heat from the combustion of 1.00 g of the given natural gas mixture.