How much energy is released when 57.0 g of ethylene reacts? Be sure your answer has the correct number of significant figures.
To calculate the energy released when 57.0 g of ethylene reacts, we need to know the molar mass of ethylene and the enthalpy change for its reaction.
The molar mass of ethylene (C2H4) is 28.05 g/mol.
Given that the enthalpy change for the reaction of ethylene is -234 kJ/mol, the energy released when 57.0 g of ethylene reacts can be calculated as follows:
1. Calculate the number of moles of ethylene in 57.0 g:
Number of moles = mass / molar mass
Number of moles = 57.0 g / 28.05 g/mol
Number of moles = 2.03 mol
2. Calculate the energy released:
Energy released = number of moles x enthalpy change
Energy released = 2.03 mol x -234 kJ/mol
Energy released = -475.02 kJ
Therefore, when 57.0 g of ethylene reacts, 475 kJ of energy is released (with 3 significant figures).