During the combustion of diesel fuel weighing 77 grams, an amount of heat equal to 784 kcal was released.

To calculate the required specific heat of combustion of diesel fuel, we apply the formula: qdt = Q / m.

The value of the variables: Q is the released amount of heat (Q = 784 kcal; in the SI system Q = 784 * 10 ^ 3 * 4.1868 J = 3282451.2 J); m is the mass of diesel fuel (m = 77 g; in the SI system m = 77 * 10-3 kg).

Let’s calculate: qdt = Q / m = 3282451.2 / (77 * 10-3) ≈ 42.629 * 10 ^ 6 J / kg or 42.629 MJ / kg.

Answer: Diesel fuel, according to the calculation, has a specific heating value of 42.629 MJ / kg.