How many tons of brown coal must be burned in order to obtain the same amount of heat as from 2.7 cubic meters. kiroshina?

To find the desired mass of brown coal, we will use the equality: qb * m1 = qk * m2 = qk * ρ * V, whence m1 = qk * ρ * V / qbu.
Constants and variables: qk – specific heat of combustion of kerosene (qk = 4.6 * 10 ^ 7 J / kg); ρ is the density of kerosene (ρ = 800 kg / m3); V is the volume of kerosene (V = 2.7 m3); qbu – specific heat of combustion of brown coal (qbu = 13 … 25 MJ / kg; we take qbu = 19 MJ / kg = 19 * 10 ^ 6 J / kg).
Calculation: m1 = qk * ρ * V / qbu = 4.6 * 10 ^ 7 * 800 * 2.7 / (19 * 10 ^ 6) = 5230 kg = 5.23 tons.