Question

Какое количество теплоты необходимо для превращения в стоградусный пар 200 г воды, взятой при температуре 40°С? Потерями энергии на нагревание окружающего воздуха пренебречь. Ответ приведите в килоджоулях.

Answer 1

Q=cmdT(нагревание до 100 С)+k(удельная теплота парообразования)m=

=4200*0.2*60+2.3*10^6*0.2=510400 Дж

Answer 2

Calculation of Heat Required to Convert 200g of Water at 40°C to Steam

To calculate the amount of heat required to convert 200g of water at 40°C to steam, we need to consider the heat required for two processes: heating the water from 40°C to its boiling point and then converting it from liquid to steam at its boiling point.

1. Heating the water from 40°C to its boiling point: - The specific heat capacity of water is approximately 4.18 J/g°C. - The temperature change is from 40°C to the boiling point of water, which is 100°C. - The mass of the water is 200g. - Using the formula Q = mcΔT, where Q is the heat energy, m is the mass, c is the specific heat capacity, and ΔT is the temperature change, we can calculate the heat required for this process.

Calculation: Q1 = mcΔT Q1 = (200g)(4.18 J/g°C)(100°C - 40°C) Q1 = 200g * 4.18 J/g°C * 60°C Q1 = 50160 J

2. Converting the water from liquid to steam at its boiling point: - The heat of vaporization for water is approximately 2260 kJ/kg. - The mass of the water is 200g (0.2 kg). - Using the formula Q = mL, where Q is the heat energy, m is the mass, and L is the heat of vaporization, we can calculate the heat required for this process.

Calculation: Q2 = mL Q2 = (0.2 kg)(2260 kJ/kg) Q2 = 452 kJ = 452000 J

3. Total heat required: - To find the total heat required, we add the heat required for both processes.

Calculation: Total heat required = Q1 + Q2 Total heat required = 50160 J + 452000 J Total heat required = 502160 J

Therefore, the amount of heat required to convert 200g of water at 40°C to steam is 502160 J, or approximately 502.16 kJ.

Please note that this calculation does not take into account energy losses to the surrounding air, as specified in the question.