Question

Сжигая 200г бензина, воду массой 8кг нагревают от 20 до 100 град. цельсия, причем часть воды испаряется. Сколько воды испарится, если КПД нагревателя=40%

Answer 1

количество тепла от сгорания бензина Q =mq =0.200*4.6*10^7=9.2*10^6 Дж

с учетом КПД  на нагревание и испарение идет Q1 =Q*КПД =9.2*10^6 *0.4 =3.68*10^6 Дж

количество тепла  на нагревание Q2 =cm(T2-T1)=4200*8(100-20)=2.688*10^6 Дж

количество тепла на испарение Q3=Q1-Q2=3.68*10^6 Дж-2.688*10^6 Дж=0,992*10^6 Дж

испарится воды Q3 =m1*L  ; m1 =Q3 /L=0,992*10^6 Дж /2.3*10^6 Дж/кг =0.431 кг = 431 г

 

ответ 431 г

Answer 2

Calculation of Water Evaporation

To calculate the amount of water that will evaporate when burning 200g of gasoline and heating 8kg of water from 20 to 100 degrees Celsius, we need to consider the efficiency of the heater.

Given that the efficiency (η) of the heater is 40%, we can calculate the energy input (Qin) into the water using the formula:

Qin = m * c * ΔT

Where: - m is the mass of water - c is the specific heat capacity of water - ΔT is the change in temperature

The energy output (Qout) from burning the gasoline can be calculated using the formula:

Qout = m_gasoline * H_gasoline

Where: - m_gasoline is the mass of gasoline - H_gasoline is the heat of combustion of gasoline

Since the efficiency of the heater is given by:

η = Qout / Qin

We can rearrange the equation to solve for Qout:

Qout = η * Qin

Now, let's calculate the amount of water that will evaporate.

Calculation Steps:

1. Calculate the energy input (Qin) into the water: - m = 8kg = 8000g (mass of water) - c = 4.2 J/g°C (specific heat capacity of water) - ΔT = 100°C - 20°C = 80°C (change in temperature) - Qin = m * c * ΔT

2. Calculate the energy output (Qout) from burning the gasoline: - m_gasoline = 200g (mass of gasoline) - H_gasoline = ? (heat of combustion of gasoline)

3. Calculate the efficiency (η) of the heater: - η = 40%

4. Calculate the amount of water that will evaporate: - Qout = η * Qin - Calculate the mass of water evaporated using the heat of vaporization of water (H_vaporization): - m_evaporated = Qout / H_vaporization

Let's calculate the values step by step.

Step 1: Calculate the energy input (Qin) into the water:

Using the formula Qin = m * c * ΔT, where m = 8000g, c = 4.2 J/g°C, and ΔT = 80°C:

Qin = 8000g * 4.2 J/g°C * 80°C Qin = 2688000 J

Step 2: Calculate the energy output (Qout) from burning the gasoline:

The heat of combustion of gasoline (H_gasoline) is not provided in the search results. Without this information, we cannot calculate the energy output accurately.

Step 3: Calculate the efficiency (η) of the heater:

Given that the efficiency (η) of the heater is 40%, we can use this value in the next step.

Step 4: Calculate the amount of water that will evaporate:

Using the formula Qout = η * Qin, where η = 40% and Qin = 2688000 J:

Qout = 0.4 * 2688000 J Qout = 1075200 J

To calculate the mass of water evaporated, we need to know the heat of vaporization of water (H_vaporization). Unfortunately, this information is not provided in the search results. Without the heat of vaporization, we cannot calculate the mass of water evaporated accurately.

In conclusion, without the heat of combustion of gasoline and the heat of vaporization of water, we cannot accurately calculate the amount of water that will evaporate in this scenario.