Combustion Energy Transfer Question?

Question

How many grams of methane [CH4(g)] must be combusted to heat 1.20 kg of water from 25.0°C to 95.0°C, assuming H2O(l) as a product and 100% efficiency in heat transfer?

I could really use some help on this one, i'm stumped!

Answer 1

Assuming a constant pressure system:

You need to find the specific heat (cp) of water. Then use the equation

delta Q = m*c* delta T

m= mass

cp= specific heat of substance at constant pressure

delta T= Temperature final- temperature initial

delta Q is what you are solving for and it is the energy needed to raise the temperature. Once you know Q, use the same equation and solve for m using the specific heat of methane instead.

Make sure you are careful to use the right units in your equation and be consistent.

If it is a constant volume, rather than constant pressure system your specific heat will be different but I would guess it is a constant pressure system based on the question you put online.