How much heat would be released by the condensation of 5.40 g of steam at 100 °C and the subsequent cooling of the water to 25 °C? [ÄHvap = 40.7 kJ/mol at 100 °C; Cp for H2O(l) is
4.18 J g-1 °C-1]
i did what u wrote above. but did not have the answer right. The answer from the book is 13.9 kJ
Heat is released by condensation steam at 100 C to water at 100 C.
q1 = mass x Hvap.
q2 = heat is released by cooling water from 100 C to 25 C.
q2 = mass x specific heat x (Tf - Ti)
where Tf is final T and Ti is initial T.
Both q1 and q2 are negative numbers.
Total heat released is q1+q2.
Check your working. Note that dHvap is per MOLE and the answer q1 will be in
kJ
whereas the answer for q2 will be in
J
Please get back if you still get the wrong answer.
why are there two q1 and q2?
wait nvm,
q1 = (5.40g/18.02g/mol)(40.7kJ/mol) = 12.20kJ
q2 = (5.40g)(4.18Jg-1°C-1)(100°C - 25°C) = 1692.9J = 1.6929kJ
q1+q2
12.20kJ + 1.6929kJ = 13.9 kJ
To calculate the heat released, we need to consider two processes: the condensation of steam to liquid water and the subsequent cooling of the water.
First, let's calculate the amount of heat released during the condensation of steam to water. The enthalpy of vaporization (ÄHvap) is given as 40.7 kJ/mol at 100 °C. We need to convert the mass of steam to moles.
Step 1: Convert the mass of steam to moles of steam.
Given: Mass of steam = 5.40 g
Molar mass of H2O = 18.02 g/mol
moles of steam = mass of steam / molar mass of H2O
moles of steam = 5.40 g / 18.02 g/mol
Step 2: Calculate the heat released during condensation.
Heat released during condensation = moles of steam × ÄHvap
Next, let's calculate the heat released during the cooling of water from 100 °C to 25 °C. We need to consider the heat capacity of water (Cp).
Step 3: Calculate the mass of water.
The mass of water remains the same throughout the cooling process, which is 5.40 g.
Step 4: Calculate the change in temperature.
Temperature change = final temperature - initial temperature
Temperature change = 25 °C - 100 °C
Step 5: Calculate the heat released during cooling.
Heat released during cooling = mass of water × Cp × temperature change
Finally, we can calculate the total heat released by adding the heat released during condensation and the heat released during cooling.
Total heat released = Heat released during condensation + Heat released during cooling
Please note that the unit conversion is essential to ensure consistent units throughout the calculations.