## 4D.3

Jessica Li 4F
Posts: 115
Joined: Fri Aug 09, 2019 12:16 am

### 4D.3

Can someone explain 4D.3b please and how to calculate the change in internal energy please? Thanks!

Ruby Tang 2J
Posts: 102
Joined: Fri Aug 30, 2019 12:15 am

### Re: 4D.3

The change in temperature should be proportional to the amount of carbon monoxide being reacted. First, convert 1.40 g of CO to moles, and you get roughly 0.0500 mol of CO. If you set up a proportion, then you get 0.0500 mol/1.00 mol = 0.636C/xC, with 0.636 being the change in temperature when 1.40 g of CO is reacted (22.799-22.113). You should get x = 13.72C, which should be the change in temperature when 1 mol of CO is reacted. From then on, you can use the total heat capacity of the calorimeter assembly: 3.00 kJ/C, and multiply it by 13.72C. The C's will cancel out and you should get -41.2 kJ (negative, because if the temperature of the surroundings is increasing, then that means the system is losing energy). When in doubt, dimensional analysis is a really valuable tool for solving this kind of problem. Hope this helps!

Jessica Li 4F
Posts: 115
Joined: Fri Aug 09, 2019 12:16 am

### Re: 4D.3

That makes a lot more sense now - thank you so much!

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