Amount if water in specific heat

Question

How many liters of water can you heat from 25 deg to 100 deg celsius using 250 gram of Methane and 250 gram of Octane Separately?

Answer 1

First, figure out how many joules of energy you need to to raise the temperature of 1 g of water from 25 to 100ºC.

q = mC∆T

q = heat = ?

m = mass of water = 1 g

C = specific heat of water = 4.184 J/gº

∆T = change in temperature = 75º

q = (1 g)(4.184 J/gº)(75º) = 313.8 J = 314 J = 0.314 kJ to raise the temperature of 1 g from 25-75º

Now you need to know how much heat is generated from burning 250 g of methane (CH₄). Looking up this value, we find it to be ~891 kJ / mole.

250 g x 1 mole / 16 g = 15.6 moles CH4

15.6 mol CH4 x 891 kJ/mol = 13,920 kJ of energy provided by 250 g methane

With this value, we can now find the g or liters of water that can be heated from 25-100º

0.314 kJ / g water x 1000 g / L = 314 kJ / liter

13,920 kJ x 1 L / 314 kJ = 44.3 L of water

You would have to look up the enthalpy of combustion for octane, and repeat the above calculation to find the liters of water.