Practice Test, Question 3A


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104969854
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Joined: Fri Sep 29, 2017 7:05 am

Practice Test, Question 3A

Postby 104969854 » Tue Feb 13, 2018 5:29 pm

How are we able to use the equation deltaS=n*C*ln T2/T1 when the question gives us grams and not moles? Our units wouldn't be able to cancel out if we cannot find the moles.

Liz White 1K
Posts: 35
Joined: Thu Jul 13, 2017 3:00 am

Re: Practice Test, Question 3A

Postby Liz White 1K » Tue Feb 13, 2018 5:35 pm

The question specifies that you have 125 grams of Krypton gas and 9.00 grams of Helium gas. Therefore, you may use the molar masses provided by a periodic table to calculate the number of moles. The molar mass of Krypton (Kr) is 83.80 g/mol and the molar mass of Helium is 4.00 g/mol.

Wayland Leung
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Joined: Sat Jul 22, 2017 3:00 am
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Re: Practice Test, Question 3A

Postby Wayland Leung » Tue Feb 13, 2018 5:43 pm

We would take the given amount of grams and divide by the molar mass of each element to obtain the number of moles of each element then plug it into the equation.


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