## 4.5

Reina Robles 2B
Posts: 71
Joined: Fri Aug 09, 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.

How do you solve this? I’m very confused. Thank you!

Paige Lee 1A
Posts: 136
Joined: Sat Sep 07, 2019 12:16 am

### Re: 4.5

Find the amount of heat transferred to ice in 0.5hrs using q=mCdeltaT. You will get 3135J transferred in 0.5 hrs. Then use dimensional analysis to find how many joules are transferred in 10hrs. You get 62.7kJ transferred in 10hrs. Then divide 62.7kJ by 8.33 moles and get 7.53kJ/mol for enthalpy of fusion

Reina Robles 2B
Posts: 71
Joined: Fri Aug 09, 2019 12:16 am

### Re: 4.5

Paige Lee 1A wrote:Find the amount of heat transferred to ice in 0.5hrs using q=mCdeltaT. You will get 3135J transferred in 0.5 hrs. Then use dimensional analysis to find how many joules are transferred in 10hrs. You get 62.7kJ transferred in 10hrs. Then divide 62.7kJ by 8.33 moles and get 7.53kJ/mol for enthalpy of fusion

That makes sense, thank you so much!