Answer
There are released a total of $226kJ$ of heat during these processes.
Work Step by Step
1. Identify the objective.
- We need to find the total energy released during these 3 processes:
a. Condensation, which we can calculate using the Heat of Vaporization.
b. Change in temperature, which we can calculate using the specific heat.
c. Freezing, which we can calculate using the Heat of Fusion.
2. Find the conversion factors and equations.
$1 kJ = 1000J$
a. Heat of Vaporization: (Water) $ = \frac{2260J}{1g}$
b. Specific Heat: (Water) $ = \frac{4.184J}{g ^{\circ}C}$
$Heat = mass \times \Delta T \times SH $
c. Heat of fusion: (Water) $= \frac{334J}{g}$
3. Calculate the heat in each process.
a. $75.0 g \times \frac{2260J}{1g} = 169500J$
b. $\Delta T = 100^{\circ}C - 0^{\circ}C = 100^{\circ}C$
$Heat = 75.0g \times 100^{\circ}C \times \frac{4.184J}{g ^{\circ}C} = 31380J$
c. $75.0 g \times \frac{334J}{1g} = 25050J$
4. Calculate the total heat, and convert the value to kJ.
$(169500J + 31380J + 25050J) \times \frac{1kJ}{1000J} = 225.93kJ$
5. Now, adjust the result to the correct number of significant figures.
Data with the lowest number of SF's : $75.0g$, with 3 significant figures.
Therefore, the result must have 3 SF's: $225.93 kJ = 226 kJ$
