The unbalanced equation for the combustion of ethanol is as follows:
C2H5OH(l) + O2(g) �¨ CO2(g) + H2O(g)
How much heat, in kJ, is liberated when 4.84 kg of C2H5OH(l) is burned?
Species Delta H�‹f (kJ/mol)
H2O(g) -241.8
CO2(g) -393.5
C2H5OH(l) -277.7
Express the answer with three significant figures.
**I balanced the equation & got this:
C2H5OH(l) + 3O2(g) �¨ 2CO2(g) + 3H2O(g)
To find the amount of heat liberated when 4.84 kg of C2H5OH(l) is burned, we can use the balanced equation and the enthalpy change of formation values.
First, convert the mass of ethanol (C2H5OH) from kilograms to grams by multiplying by 1000:
4.84 kg × 1000 g/kg = 4840 g
Next, calculate the moles of C2H5OH by dividing the mass by the molar mass of C2H5OH. The molar mass of C2H5OH is the sum of the molar masses of carbon (C), hydrogen (H), and oxygen (O) in the compound:
C: (1 × 12.01 g/mol) = 12.01 g/mol
H: (5 × 1.01 g/mol) = 5.05 g/mol
O: (1 × 16.00 g/mol) = 16.00 g/mol
Molar mass of C2H5OH = 12.01 g/mol + 5.05 g/mol + 16.00 g/mol + 1.01 g/mol = 34.07 g/mol
Moles of C2H5OH = 4840 g ÷ 34.07 g/mol
Next, we can use the stoichiometric coefficients from the balanced equation to determine the moles of CO2 and H2O produced when 1 mole of C2H5OH is burned. From the balanced equation:
1 mole of C2H5OH produces 2 moles of CO2 and 3 moles of H2O
So the moles of CO2 produced = moles of C2H5OH × 2
And the moles of H2O produced = moles of C2H5OH × 3
Now, we can calculate the amount of heat liberated using the enthalpy change of formation values. The enthalpy change of formation (ΔHf) for a substance is the amount of heat released or absorbed when 1 mole of that substance is formed from its elements in their standard state.
Given ΔHf values:
ΔHf(C2H5OH) = -277.7 kJ/mol
ΔHf(CO2) = -393.5 kJ/mol
ΔHf(H2O) = -241.8 kJ/mol
The amount of heat liberated when 1 mole of C2H5OH is burned can be calculated using the ΔHf values for the products and reactants. From the balanced equation, we can see that 1 mole of C2H5OH produces 2 moles of CO2 and 3 moles of H2O.
So, the heat liberated per mole of C2H5OH burned = (2 mol of CO2 × ΔHf(CO2)) + (3 mol of H2O × ΔHf(H2O))
To calculate the amount of heat liberated when 4.84 kg of C2H5OH is burned, we can multiply the moles of C2H5OH by the heat liberated per mole of C2H5OH burned.
Finally, convert the result to kilojoules (kJ) with three significant figures.
delta Hreaction = (n*deltaHProducts) - (n*delta H reactants)
Then delta Hrxn x (4.84/molar mass ethanol)