2CH3OH(g)→2CH4(g)+O2(g)ΔH=+252.8kJ
How many kilojoules of heat are released when 38.8g of CH4(g) reacts completely with O2(g) to form CH3OH(g) at constant pressure?
To determine the amount of heat released in the reaction, we first need to calculate the amount of moles of CH4(g) involved in the reaction, using the given mass of CH4(g) and its molar mass.
Step 1: Calculate the number of moles of CH4(g)
Given mass of CH4(g) = 38.8g
Molar mass of CH4(g) = 16.04g/mol (carbon: 12.01g/mol + hydrogen: 1.01g/mol x 4)
Number of moles of CH4(g) = Mass / Molar mass
Number of moles of CH4(g) = 38.8g / 16.04g/mol
Number of moles of CH4(g) ≈ 2.42 mol
Step 2: Apply the stoichiometry of the reaction to determine the amount of heat released.
According to the balanced chemical equation, 2 moles of CH4(g) react to produce 252.8 kJ of heat. Therefore, 1 mole of CH4(g) will release 252.8 kJ / 2 moles.
Amount of heat released = (Number of moles of CH4(g) / 2 moles) * 252.8 kJ
Amount of heat released = (2.42 mol / 2 mol) * 252.8 kJ
Amount of heat released ≈ 243.8 kJ
Therefore, when 38.8g of CH4(g) reacts completely with O2(g) to form CH3OH(g) at constant pressure, approximately 243.8 kJ of heat is released.