looking for minimum mass of methane?

Question

Using a molar heat of combustion of –890 kJ/mol, The minimum mass of methane that must be burned to warm 5.64 kg of water from 21.5°C to 77.4°C, assuming no heat losses to the environment is ab.c? g.

Put your answer for ab.c in grams

Answer 1

First find out how much heat is needed to raise the temperature of 5.64 kg of water from 21.5 to 77.4 degrees. Then determine moles and mass of methane required to provide that amount of heat.

1. q = mC∆T = (5.64 kg)(4.184 kJ/kg/deg)(77.4-21.5) = kJ heat needed
2. kJ heat needed x 1 mol methane/890 kJ x 16 g/mole methane = g methane required