The heating and subsequent vaporization of alcohol consumed 105 kJ of energy.

The heating and subsequent vaporization of alcohol consumed 105 kJ of energy. Determine the mass of alcohol if its initial temperature is 18 degrees?

Initial data: Q (consumed energy) = 105 kJ = 105 * 10 ^ 3 J; t (initial temperature) = 18 ºС; tк (boiling point, ethyl alcohol) = 78.3 ºС.

Constants: C (specific heat of alcohol) = 2500 J / (kg * K); L (specific heat of vaporization of alcohol) = 0.9 * 10 ^ 6 J / kg.

We express the mass of alcohol from the following formula:

Q = C * m * (tк – t) + L * m = m * (C * (tк – t) + L).

m = Q / (C * (tк – t) + L).

Let’s perform the calculation:

m = 105 * 10 ^ 3 / (2500 * (78.3 – 18) + 0.9 * 10 ^ 6) = 0.1 kg or 100 g.