How many kilojoules of heat are released when 38.9 g of CH4(g) reacts completely with O2(g) to form CH3OH(g) at constant pressure?
Express your answer with the appropriate units.
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To calculate the heat released in the reaction, we first need to write and balance the chemical equation for the reaction:
CH4(g) + 2O2(g) -> CH3OH(g) + H2O(g)
Next, we calculate the molar masses of each compound:
CH4 = 16.05 g/mol
O2 = 32.00 g/mol
CH3OH = 32.04 g/mol
Now we can calculate the moles of CH4:
38.9 g / 16.05 g/mol = 2.425 mol
From the balanced chemical equation, we see that 1 mol of CH4 produces 1 mol of CH3OH. Therefore, 2.425 mol of CH4 will produce 2.425 mol of CH3OH.
Now we calculate the heat released in the reaction using standard enthalpy of formation values:
ΔHf°(CH4) = -74.87 kJ/mol
ΔHf°(CH3OH) = -201.0 kJ/mol
ΔHf°(O2) = 0 kJ/mol
ΔHf°(H2O) = -241.8 kJ/mol
ΔH°rxn = ΣnΔHf°(products) - ΣmΔHf°(reactants)
ΔH°rxn = [2.425(-201.0 kJ/mol) + 1(-241.8 kJ/mol)] - [2(-74.87 kJ/mol) + 2(0 kJ/mol)]
ΔH°rxn = -700.16 kJ
Therefore, 700.16 kJ of heat are released when 38.9 g of CH4(g) reacts completely with O2(g) to form CH3OH(g) at constant pressure.
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