Water weighing 100 g from a beaker was poured into a vessel heated by the flame of an alcohol lamp and evaporated.

| June 16, 2021 | education

Water weighing 100 g from a beaker was poured into a vessel heated by the flame of an alcohol lamp and evaporated. Calculate the mass of alcohol burned. The heating of the vessel and the losses for heating the air can be neglected.

1) Water from an initial room temperature of 20 degrees to a boiling point of water of 100 degrees will absorb energy Q, where the general formula for calculating the amount of heat consumed: Q = m • c • Δt for a mass of 0.1 kg; temperature change Δt = (t2 – t1) = 80 (degrees); for water Q = 0.1 • 4200 • 80 = 33600 (J);
2) If the losses are neglected, then the energy released by the spirit lamp was all used to heat the water: Q = q • m, where the tabular value is the specific heat of combustion of alcohol q = 27,000,000 J / kg. Let us find the mass of alcohol m = Q: q, m = 33600: 27,000,000 = 0.00124 kg = 1.24 g.



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