Ethanol, C2H5OH is mixed with gasoline and sold as gasohol. Use the following to calculate the grams of ehanol needed to provide 293 kJ of heat.
C2H5OH + 3O2 ----> 2CO2 + 3H2O
Delta H = -1235 kJ
How do I do this question
The balanced equation shows that 1 mol C2H5OH provides 1235 kJ of energy. 1 mol C2H5OH = how many grams? I think that is about 46 but you should confirm that.
So 46 g C2H5OH provides 1235 kJ. You want 293 kJ. It's a simple proportion.
To solve this question, we need to use the given information and apply the concept of stoichiometry to calculate the grams of ethanol required to provide 293 kJ of heat.
First, let's convert the given delta H value from kilojoules (kJ) to joules (J). Since there are 1000 J in 1 kJ, we can multiply the delta H value by 1000:
Delta H = -1235 kJ * 1000 = -1,235,000 J
Now, we can set up a ratio based on the stoichiometry of the balanced chemical equation. According to the equation, 1 mole of C2H5OH produces -1,235,000 J of heat.
The molar mass of C2H5OH can be calculated by adding up the atomic masses of each element:
C = 12.01 g/mol
H = 1.01 g/mol (there are 6 Hydrogen atoms in ethanol)
O = 16.00 g/mol (there are 1 Oxygen atom in ethanol)
Molar mass of C2H5OH = (2 * C) + (6 * H) + O = (2 * 12.01 g/mol) + (6 * 1.01 g/mol) + 16.00 g/mol = 46.07 g/mol
To calculate the grams of ethanol needed to provide 293 kJ of heat, we need to use the following steps:
1. Convert the given heat value from joules to kilojoules:
Heat = 293 kJ * 1000 = 293,000 J
2. Calculate the number of moles of ethanol by dividing the given heat in joules by the delta H value:
Number of moles = Heat / Delta H = 293,000 J / -1,235,000 J/mol = -0.2371 mol (always use the absolute value)
3. Convert the number of moles to grams by multiplying with the molar mass of ethanol:
Grams of ethanol = Number of moles * Molar mass = -0.2371 mol * 46.07 g/mol = -10.92 g (always use the absolute value)
Since mass cannot be negative, we take the absolute value of the calculated value, which gives us the final result:
The grams of ethanol needed to provide 293 kJ of heat is approximately 10.92 g.