calorimetry: burning methane to heat water

Question

“Burning methane releases 890.4kJ/mol of methane burned. In a hot water tank, natural gas (primarily methane) is burned to release heat and warm up the water. What mass of methane would need to be burned to warm up 60 US gallons of water from 12.0°C to 75°C?”

I know that:

q=mc delta t

m=?

T_i= 12.0°C

T₂= 75.0°C

q= 890.4 kJ/mol

I’m not sure about c though, should it be water or methane?

Answer 1

Hi Anja

Actually it is the c for water that you need. And you need the heat of combustion for methane (890.4) The basic equation is

Q(out)(methane) = Q(in)(water)

Use mc delta T for the water (make sure you use the right mass for the water) to find the heat reqd to warm the water

Then take that q in an equation for the methane, using the heat of combustion for methane and calculate that mass.