Multiple Choice
If 24.0 grams of carbon monoxide (CO) undergoes complete oxidation to form carbon dioxide (CO2), how much heat is released, assuming the reaction is exothermic? The balanced equation is: 2CO(g) + O2(g) → 2CO2(g), ΔH = -566 kJ/mol.
8. Thermochemistry
Thermochemical Equations
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Nitromethane (CH3NO2), sometimes used as a fuel for drag racing, burns according to the following reaction:
4 CH3NO2 (l) + 7 O2 (g) → 4 CO2 (g) + 6 H2O (g) + 4 NO2 (g) ∆Hº = – 2441.6 kJ
How much heat is released by burning 125.0 g of nitromethane (MW:61.044 g/mol)?
A
1.250 x 103 kJ
B
-1.250 x 103 kJ
C
2.440 x 103 kJ
D
-2.440 x 103 kJ
Verified step by step guidance1
First, determine the number of moles of nitromethane (CH3NO2) in 125.0 g. Use the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \). The molar mass of nitromethane is 61.044 g/mol.
Calculate the moles of nitromethane: \( \text{moles of CH3NO2} = \frac{125.0 \text{ g}}{61.044 \text{ g/mol}} \).
Next, use the stoichiometry of the reaction to determine the heat released. The reaction shows that 4 moles of CH3NO2 release 2441.6 kJ of heat.
Set up a proportion to find the heat released by the moles of nitromethane calculated: \( \text{heat released} = \left( \frac{\text{moles of CH3NO2}}{4 \text{ moles}} \right) \times 2441.6 \text{ kJ} \).
Finally, ensure the sign of the heat released is negative, as the reaction is exothermic, meaning heat is released.
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