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The molar mass of a substance is simply the mass of one mole of its entities (atoms, molecules, etc.). It is calculated by summing the atomic masses of all the atoms present in a molecule. For ethanol, which has the molecular formula \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{OH}\), we need the atomic masses of carbon, hydrogen, and oxygen.
The atomic mass of carbon is 12.01 g/mol, hydrogen is 1.01 g/mol, and oxygen is 16.00 g/mol. Ethanol consists of two carbon atoms, six hydrogen atoms, and one oxygen atom. To find the molar mass, we multiply the number of each type of atom by their respective atomic masses, and then add those values together:

• Carbon: \(2 \times 12.01 \, \text{g/mol} = 24.02 \, \text{g/mol}\)
• Hydrogen: \(6 \times 1.01 \, \text{g/mol} = 6.06 \, \text{g/mol}\)
• Oxygen: \(1 \times 16.00 \, \text{g/mol} = 16.00 \, \text{g/mol}\)

Adding these up gives you the molar mass of ethanol, which is 46.07 g/mol.

Stoichiometry is the aspect of chemistry that involves calculating the quantitative relationships of reactants and products in a chemical reaction. It allows us to determine how much of a substance is consumed or produced.
In the context of the combustion of ethanol, we want to find out how many moles of ethanol are involved. Since the problem states that 235.0 g of ethanol are combusted, and we've calculated the molar mass to be 46.07 g/mol, conversion is straightforward:

We use the formula: \[\text{Moles of ethanol} = \frac{\text{Mass of ethanol}}{\text{Molar mass of ethanol}}\]
Substituting the values in: \[\frac{235.0 \, \text{g}}{46.07 \, \text{g/mol}} = 5.10 \, \text{moles}\]
Doing stoichiometric calculations ensures correct proportions of reactants and products, which is crucial in practical applications like energy production.

Energy conversion during a chemical reaction such as combustion involves transforming chemical energy stored in bonds to heat or other forms of energy. For ethanol, the combustion process releases heat as ethanol reacts with oxygen to form carbon dioxide and water.

Combustion of ethanol is an exothermic reaction, meaning it releases energy. As specified, the combustion of one mole of ethanol releases 1367 kJ. Thus, knowing the number of moles combusted, we multiply by the energy per mole to calculate total energy released.
For 5.10 moles of ethanol combusted, the heat produced is:\[5.10 \, \text{moles} \times 1367 \, \frac{\text{kJ}}{\text{mole}} = 6971.7 \, \text{kJ}\]
This process highlights the principles of energy conversion and conservation, providing insight into how chemical reactions can be utilized to produce energy for practical uses, such as in heating and powering engines.