## 4.5

Grace Jansen 2A
Posts: 28
Joined: Sat Jul 20, 2019 12:16 am

### 4.5

In 1750, Joseph Black performed an experiment that eventually led to the discovery of enthalpies of fusion. He placed two samples of water, each of mass 150. g, at 0.00 8C (one ice and one liquid) in a room kept at a constant temperature of 5.00 8C. He then observed how long it took for each sample to reach its final temperature. The liquid sample reached 5.00 8C after 30.0 min. However, the ice took 10.5 h to reach 5.00 8C. He concluded that the difference in time that the two samples required to reach the same final temperature repre- sented the difference in heat required to raise the temperatures of the samples. Use Black’s data to calculate the enthalpy of fusion of ice in kilojoules per mole. Use the known heat capacity of liquid water.

In the solutions manual, they divide 10 hours by 0.5 hours. Why do they divide the times?

Paul Hage 2G
Posts: 105
Joined: Thu Jul 25, 2019 12:17 am

### Re: 4.5

From the values given in the problem, we can calculate the heat absorbed in 30 minutes. Therefore, assuming the heat absorption rate is constant, we can find the heat absorbed in 10 hours. 10/0.5=20, so to find the heat absorbed in 10 hours, you would multiply the heat absorbed in 30 minutes by 20.