Question

1. If 5.0g of CH4 react, how much H₂O will be formed?

2. If 5.0 g of CH₄ reacted,how much energy would be released or absorbed?

Answer 1

This is most likely the combustion of CH4

so

CH4 + O2 = CO2 + H2O

balance H, then O

CH4 + 2O2 = CO2 + 2H2O

now...

ratio is

16 g of CH4 = 1 mol

5 g of CH4 = x

x = 5/16 = 0.3125 mol of CH4

1 mol of CH4 = 2 mol of H2O

0.3125 mol --> 2*0.3125 = 0.625 mol of H2O

mass = mol*MW = 0.625*18 = 11.25 g of H2O

Q2.

Get enthalpy of combustion

HRxn = Hprod - HReact = (CO2 + 2H2O) - (CH4 + 2O2)

HRxn = -393.5 + 2*(-241.8) - (-74.6 + 2*0)

HRxn = -802.5 kJ/mol

Then,

1 mol of CH4 = 802.5 kJ/mol

0.3125 mol --> 0.3125 *802.5 = 250.781 kJ/ released