How much coal must be taken to heat 2 kg water from 20 degrees to the boiling point?
| June 16, 2021 | education
Task data: m1 (mass of heated water) = 2 kg; t0 (initial temperature) = 20 ºС.
Constant data: q (specific heat of combustion of coal) = 2.7 * 10 ^ 7 J / kg; Sv (specific heat of water) = 4200 J / (kg * K); tboil (boiling point) = 100 ºС.
We express the sought mass of spent coal from the equality: q * m2 = Sv * m1 * (tboil – t).
Calculation: m2 = 4200 * 2 * (100 – 20) / (2.7 * 10 ^ 7) = 0.0249 kg (24.9 g).
Answer: You need to take 24.9 g of coal.
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