How many kJ will be released as 575 g of steam at 176 degrees celsius are changed into ice at -75 degrees celsius?
q1 = heat released to move steam from 176 C to 100 C.
q1 = mass steam x specific heat x (Tfinal-Tinitial) where Tinitial = 176 and Tfinal = 100.
q2 = heat released to condense steam
@ 100 C to liquid water @ 100 C.
q2 = mass steam x heat vaporization
q3 = heat released to move temperature liquid water from 100 C to 0 C.
q3 = mass water x specific heat water x (Tfinal-Tinitial).
q4 = heat released to change liquid water @ 0 C to solid water @ 0 C.
q4 = mass water x heat fusion.
q5 = heat released to move solid water (ice) from zero C to -75 C.
q5 = mass ice x specific heat ice x (Tfinal-Tinitial).
Total Q = q1 + q2 + q3 + q4 + q5, then change J to kJ.
To calculate the amount of energy released when steam is changed into ice, we can use the following equation:
Q = m * ΔH
where:
Q is the amount of energy released or absorbed (in joules),
m is the mass of the substance (in grams), and
ΔH is the enthalpy change (in joules per gram).
In this case, we need to find the amount of energy released when 575 g of steam is changed into ice. We can break down the problem into two steps:
Step 1: Calculate the energy released when steam is cooled from 176°C to 0°C:
Q1 = m1 * ΔH1
To find Q1, we first need to calculate the mass of the steam that is cooled from 176°C to 0°C. This can be done by multiplying the mass of the steam (575 g) by the specific heat capacity of steam (Cp_steam), which is the amount of energy required to raise the temperature of 1 gram of steam by 1 degree Celsius.
Next, we need to calculate the enthalpy change (ΔH1) during this process. The enthalpy change of steam cooling from its initial temperature (176°C) to its boiling point (100°C) can be obtained from steam tables or specific heat capacity tables.
Step 2: Calculate the energy released when the steam is further cooled from 0°C to -75°C and changed into ice:
Q2 = m2 * ΔH2
To find Q2, we first need to calculate the mass of the water that is cooled from 0°C to -75°C. For this, we start with the mass of the steam (since steam and water have the same mass), and subtract the mass of steam that is condensed when it is cooled from 176°C to 0°C.
Next, we need to calculate the enthalpy change (ΔH2) during this process. The enthalpy change of water cooling from 0°C to its freezing point (0°C) and then changing into ice at 0°C can also be obtained from tables.
Finally, we can find the total amount of energy released (Q_total) by summing up Q1 and Q2:
Q_total = Q1 + Q2
To convert the energy from joules to kilojoules, divide the result by 1000.
Please note that the specific heat capacities and enthalpy changes may vary depending on the pressure conditions, so it's essential to use appropriate values from reliable sources or tables for accurate calculations.