C2H5OH(l) + 3 O2(g) -> 2 CO2(g) + 3 H2O(g)
During an experiment 10.00 g of ethanol is completely
burned in air to release CO2(g) and H2O(g) as shown in
the equation above. During the combustion, 296.6 kJ of
heat energy is released. What is the molar enthalpy of
combustion, H˚comb?
(A) –2966 kJ•mol–1
(B) –1366 kJ•mol–1
(C) –64.36 kJ•mol–1
(D) –29.66 kJ•mol–1
I am unsure on how B is the correct answer. I have never been taught over this, I am preparing for Chemolympiad.
C2H5OH + 3O2 ==> 2CO2 + 3H2O
delta Hcomb = -296.6 kJ.
So you have 296.6 kJ released for 10 g; you want to know how much is released for 1 mol (46.07g); therefore,
dH = -296.6 x 46.07/10 = ?
Ah, the joys of combustion and molar enthalpy! Let me help you with this.
In this problem, we need to find the molar enthalpy of combustion (ΔH˚comb) for ethanol. The given equation represents the combustion reaction, where ethanol (C2H5OH) reacts with oxygen (O2) to form carbon dioxide (CO2) and water (H2O).
To start, we need to convert the given mass of ethanol (10.00 g) to moles. The molar mass of ethanol is 46.07 g/mol.
10.00 g ethanol * (1 mol/46.07 g) = 0.217 mol ethanol
Now, let's find the amount of heat released during the combustion. The equation tells us that 296.6 kJ of heat energy is released.
Next, we'll calculate the molar enthalpy of combustion by dividing the amount of heat released by the number of moles of ethanol combusted.
ΔH˚comb = (296.6 kJ) / (0.217 mol)
Calculating this gives us ΔH˚comb ≈ -1366 kJ/mol.
So, the correct answer is (B) –1366 kJ•mol–1. Now you can continue clowning around your Chemolympiad preparation!
To find the molar enthalpy of combustion (ΔH˚comb), we need to use the given information and the equation for the combustion of ethanol.
The balanced equation is:
C2H5OH(l) + 3 O2(g) -> 2 CO2(g) + 3 H2O(g)
From the equation, we can see that 2 moles of CO2 are produced for every mole of C2H5OH burned. Therefore, we need to determine the number of moles of ethanol burned.
First, we need to convert the mass of ethanol (10.00 g) to moles using its molar mass.
The molar mass of ethanol (C2H5OH) is:
Molar mass of C: 12.01 g/mol
Molar mass of H: 1.01 g/mol
Molar mass of O: 16.00 g/mol
Molar mass of C2H5OH = (2 * 12.01) + (6 * 1.01) + 16.00 = 46.07 g/mol
Now, we can calculate the moles of ethanol burned:
moles of ethanol = mass of ethanol / molar mass of ethanol
moles of ethanol = 10.00 g / 46.07 g/mol
Next, we have to determine the heat energy released during the combustion of the given amount of ethanol.
Given: 296.6 kJ
To find the molar enthalpy of combustion (ΔH˚comb), we divide the heat energy released by the number of moles of ethanol burned:
ΔH˚comb = heat energy released / moles of ethanol
ΔH˚comb = 296.6 kJ / (10.00 g / 46.07 g/mol)
ΔH˚comb = 296.6 kJ / (0.217 mol)
Finally, we can calculate the value of ΔH˚comb:
ΔH˚comb ≈ -1366 kJ/mol
Therefore, the correct answer is (B) -1366 kJ•mol–1.
To determine the molar enthalpy of combustion, ΔH°comb, we need to use the equation:
ΔH°comb = (energy released) / (moles of substance burned)
First, we need to calculate the moles of ethanol burned.
Step 1: Convert grams to moles of ethanol using the molar mass of ethanol.
The molar mass of ethanol (C2H5OH) can be calculated as follows:
(2 × atomic mass of carbon) + (6 × atomic mass of hydrogen) + atomic mass of oxygen + atomic mass of hydrogen
(2 × 12.01 g/mol) + (6 × 1.01 g/mol) + 16.00 g/mol + 1.01 g/mol = 46.07 g/mol
moles of ethanol = (mass of ethanol) / (molar mass of ethanol)
moles of ethanol = 10.00 g / 46.07 g/mol ≈ 0.217 mol
Step 2: Calculate the molar enthalpy of combustion.
ΔH°comb = (energy released) / (moles of substance burned)
ΔH°comb = 296.6 kJ / 0.217 mol
ΔH°comb ≈ -1366 kJ/mol (rounded to the nearest whole number)
Therefore, the correct answer is option (B) –1366 kJ•mol–1.