With the complete combustion of 2 kg of anthracite, 60 MJ of heat is released.

With the complete combustion of 2 kg of anthracite, 60 MJ of heat is released. How much anthracite should be burned to get 45 kJ of heat.

Given:

m1 = 2 kilograms is the mass of anthracite;

Q1 = 60 MJ = 60 * 10 ^ 6 Joules – the amount of energy released during the complete combustion of anthracite of mass m1;

Q2 = 45 kJ = 45 * 10 ^ 3 Joules – the required amount of heat.

It is required to determine m2 (kilogram) – how much anthracite must be burned in order to obtain an amount of heat equal to Q2.

Let’s determine the specific heat of combustion of anthracite:

q = Q1 / m1 = 60 * 10 ^ 6/2 = 30 * 10 ^ 6 Joule / kilogram.

Then, the amount of anthracite required for combustion will be equal to:

m2 = Q2 / q = 45 * 10 ^ 3 / (30 * 10 ^ 6) = 1.5 * 103 ^ – 6 = 1.5 * 10 ^ -3 = 0.0015 kilograms.

Answer: to get 45 kJ of heat, it is necessary to burn anthracite weighing 0.0015 kilograms.