) Consider the reaction, C2H4(g) + H2(g) → C2H6(g), where ΔH = –137 kJ. How many kilojoules are released when 55.3 g of C2H4 reacts?
To find the number of kilojoules released when 55.3 g of C2H4 reacts, we first need to calculate the moles of C2H4 involved in the reaction.
1. Calculate the molar mass of C2H4:
Molar mass of C = 12.01 g/mol
Molar mass of H = 1.008 g/mol
Molar mass of C2H4 = 2(12.01) + 4(1.008) = 28.054 g/mol
2. Calculate the moles of C2H4 in 55.3 g:
moles = mass / molar mass
moles = 55.3 g / 28.054 g/mol ≈ 1.972 mol
3. Since the reaction involves 1 mole of C2H4, the number of kilojoules released can be calculated from the given ΔH value:
ΔH = -137 kJ/mol
4. Calculate the kilojoules released when 1.972 mol of C2H4 reacts:
ΔH = -137 kJ/mol
kJ released = 137 kJ/mol * 1.972 mol ≈ -269.964 kJ
Therefore, approximately 269.964 kJ are released when 55.3 g of C2H4 reacts.