Gasohol contains ethanol (C2H4OH)(l), which when burned reacts with oxygen to produce CO2(g) and H2O(g). How much heat is released when 12.5g of ethanol burns?
C2H5OH(l) + 3 O2(g) --> 2 CO2(g) + 3H2O(l)
Delta H = -1368kJ
Chemistry - DrBob222, Wednesday, May 19, 2010 at 9:34pm
You get 1368 kJ when 1 mole (46 g) is burned; how much will you get when you burn 12.5 g?
I don't know how you would solve this. :(
Let's try something different.
You get 1368 kJ for a mol of C2H5OH. How many moles C2H5OH do you have in 12.5 g C2H5OH?
Then 1368 kJ/mol x mol = ?? kJ.
1760kj
To calculate the amount of heat released when 12.5 g of ethanol burns, we need to use the given information about the molar mass of ethanol and the enthalpy change of the reaction. Here's how you can solve it step by step:
1. Calculate the number of moles of ethanol in 12.5 g using the equation:
Moles = mass / molar mass
The molar mass of ethanol (C2H5OH) is calculated as:
(2 x molar mass of carbon) + (6 x molar mass of hydrogen) + (1 x molar mass of oxygen)
= (2 x 12.01 g/mol) + (6 x 1.01 g/mol) + (1 x 16.00 g/mol)
= 46.07 g/mol
Moles = 12.5 g / 46.07 g/mol
2. Calculate the heat released per mole of ethanol burned using the given enthalpy change:
Heat released per mole = ΔH / Stoichiometric coefficient of ethanol
ΔH = -1368 kJ (given)
Stoichiometric coefficient of ethanol = 1 (from the balanced equation)
Heat released per mole = -1368 kJ / 1
3. Calculate the heat released when 12.5 g of ethanol burns:
Heat released = Heat released per mole x Moles
Heat released = (-1368 kJ) x (moles)
Substitute the value of moles from step 1 into the equation.
Heat released = (-1368 kJ) x (moles)
4. Plug in the calculated values and compute.
Heat released = -1368 kJ x (12.5 g / 46.07 g/mol)
Heat released = -1368 kJ x 0.271 mol
Heat released = -371.928 kJ (rounded to three significant figures)
Therefore, approximately 371.9 kJ of heat is released when 12.5 g of ethanol burns.