Question

Сколько водяного пара, температура которого 100 градусов надо ввести в калориметр, чтобы 150 г снега растаяло. Нач. температура снега -20 градусов. Потери тепла составляют 30 процентов. Срочно

Answer 1

дано

Т=0 С

T1=100 C

L= 2.3*10^6 Дж/кг

C1=4200 Дж/кг*С

С2=2100 Дж/кг*С

λ = 3.4*10^5 Дж/кг

m2=150 г  -  можно не переводить в кг - на вычисления не влияет

Т2= -20 С

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m1 -?

 

решение

по условию -лед полностью растаял-конечная температура процесса  Т=0 С

Q1 =C2*m2*(T-T2) - лед нагревается  - поглощает тепло

Q2 =λ*m2               - лед плавится - поглощает тепло

Q3 = - Lm1                - пар конденсируется - отдает тепло

Q4 =C1*m1*(T-T1) - вода остывает - отдает тепло

уравнение теплового баланса

Q1+Q2+Q3+Q4=0

C2*m2*(T-T2) + λ*m2 - Lm1 +C1*m1*(T-T1) = 0

m2 (C2*(T-T2) + λ) - m1 (L - C1*(T-T1) ) = 0

m2 (C2*(T-T2) + λ) =  m1 (L - C1*(T-T1) )

m1 = m2 (C2*(T-T2) + λ) / (L - C1*(T-T1) )

m1 = 150 (2100(0-(-20))+3.4*10^5) /  (2.3*10^6 -4200(0-100))= 21.066 =21 г

 

Answer 2

Calculation of the Amount of Steam Required

To calculate the amount of steam required to melt 150 g of snow, we need to consider the initial temperature of the snow, the heat losses, and the final temperature of the snow.

Given: - Initial temperature of the snow: -20 degrees Celsius - Final temperature of the snow: 0 degrees Celsius (since the snow will melt) - Heat losses: 30% (which means 70% of the heat will be transferred to the snow)

To find the amount of steam required, we can use the formula:

Q = m * c * ΔT

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

First, let's calculate the heat transferred to the snow:

Q = 150 g * c * (0 - (-20))

We know that the specific heat capacity of water is approximately 4.18 J/g°C. Substituting this value, we get:

Q = 150 g * 4.18 J/g°C * (0 - (-20))

Simplifying the equation:

Q = 150 g * 4.18 J/g°C * 20°C

Q = 12540 J

Since the heat losses are 30%, only 70% of the heat will be transferred to the snow. Therefore, the amount of heat actually transferred to the snow is:

Q_actual = 0.7 * Q

Q_actual = 0.7 * 12540 J

Q_actual = 8778 J

Now, let's calculate the amount of steam required. We know that the heat transferred to the snow is equal to the heat gained by the steam:

Q_actual = m_steam * c_steam * ΔT_steam

We need to find the mass of steam (m_steam) and the change in temperature of the steam (ΔT_steam).

The specific heat capacity of steam is approximately 2.03 J/g°C. Substituting this value, we get:

8778 J = m_steam * 2.03 J/g°C * ΔT_steam

To find the mass of steam, we rearrange the equation:

m_steam = 8778 J / (2.03 J/g°C * ΔT_steam)

We don't have the value of ΔT_steam, so we cannot calculate the exact mass of steam required without this information.

Please provide the change in temperature of the steam so that we can calculate the mass of steam required.