[GregoryC4]

Hey guys, I'm having some trouble figuring out some of these Calorimetry questions. I worked at it for a bit and tried to think of it logically but could not get it. So far, I figured out the energy required to heat the water to 98°C, but I'm stuck there.
Any help would be much appreciated  .

QUESTION:

What mass of methane (CH4(g)) needs to be burned to heat 300 mL of water from 23.0 oC to the boiling point (98.0 oC)? (ΔHcombustion = -639 kJ/mol; specific heat of water = 4.18 J/goC)

[Borek]

If you know how much energy you need, simple ratio would be enough to calculate number of moles of methane that you need to burn.

[GregoryC4]

If you know how much energy you need, simple ratio would be enough to calculate number of moles of methane that you need to burn.

Could you please explain what you mean by ratio a bit more? The ΔH combustion = -639 kJ/mol is the amount of heat the CH₄ produced right? So how do I put everything together to get the amount of CH₄ needed to heat the water up amount of energy I calculated?

[Borek]

The ΔH combustion = -639 kJ/mol is the amount of heat the CH₄ produced right?

Per 1 mole of CH₄ burnt.

How much per 0.5 moles?

How much per 0.25 moles?

How much you need? How many moles will produce that?