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 needs to be burned to release 15 MJ of energy?

1) Action decision.

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

Q1 = q * m1, where, according to the condition of the problem, Q1 (released heat) = 60 MJ or 60 * 10 ^ 6 J, m1 (burnt anthracite) = 2 kg.

q = Q1 / m1 = 60 * 10 ^ 6/2 = 30 * 10 ^ 6 J / kg.

Let’s calculate the mass of anthracite with an energy release of 15 MJ (Q2 = 15 * 10 ^ 6 J).

m2 = Q2 / q = 15 * 10 ^ 6/30 * 10 ^ 6 = 0.5 kg.

2) Proportion.

Q1 / m1 = Q2 / m2.

m2 = Q2 * m1 / Q1 = 15 * 2/60 = 30/60 = 0.5 kg.

Answer: You need to burn 0.5 kg of anthracite.