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
How do I solve this problem?
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gang
To solve this problem, we need to use the given information about the chemical reaction and the enthalpy change. The enthalpy change, represented as ΔH, tells us the amount of heat released or absorbed during a reaction.
Step 1: Determine the molar mass of ethanol (C2H5OH).
The molar mass of ethanol (C2H5OH) can be calculated by adding up the atomic masses of each element multiplied by the number of atoms in the compound.
C: 12.01 g/mol
H: 1.01 g/mol x 6 (6 hydrogen atoms in ethanol)
O: 16.00 g/mol
Molar mass of ethanol: 12.01 g/mol + 1.01 g/mol x 6 + 16.00 g/mol = 46.07 g/mol
Step 2: Calculate the number of moles of ethanol (C2H5OH).
Given mass of ethanol: 12.5 g
Number of moles of ethanol = mass / molar mass
Number of moles of ethanol = 12.5 g / 46.07 g/mol ≈ 0.271 moles
Step 3: Use the stoichiometry of the chemical reaction to determine the amount of heat released.
From the balanced chemical equation, the stoichiometric ratio between ethanol and heat released (ΔH) is 1:1368 kJ.
Therefore, the heat released for 0.271 moles of ethanol is calculated as follows:
Heat released = moles of ethanol x ΔH
Heat released = 0.271 moles x -1368 kJ/mol
The negative sign (-) indicates that the reaction is exothermic.
Calculating the heat released:
Heat released = -370.728 kJ
Therefore, when 12.5 g of ethanol burns, approximately 370.728 kJ of heat is released.