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Author Topic: General chemistry help with gases?  (Read 3963 times)

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Nhockeyfreak

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General chemistry help with gases?
« on: March 01, 2009, 01:07:10 PM »

1. All of the following equations are statements of the ideal gas law except
A. R=PV/nT
B. PV/T=nR
C. P/n=RT/v
d. P=nRTV
2. In Graham's equation, the square roots of the molar masses can be substituted with the square roots of the
a. compressibilities
b. molar volumes
c. gas densities
d. gas constants
3.An ideal gas is an imaginary gas
a. that conforms to all of the assumptions of the kinetic theory
b. whose particles have zero mass
c. not made of particles
d. made of motionless particles
4. According to the kinetic molecular theory, gases condense into liquids because of
a. elastic collisions
b. gravity
c. atmospheric pressure
d. forces between molecules
5. Chlorine is produced by the reaction 2HCI->H subscript 2 + CI subscript 2. How mnay grams of HCI (3.65 g/mol) must be used to produce 10 L of chlorine at STP?
a. 15.8 g
b. 32.6 g
c. 30.2 g
d. 36.5 g
6. A sample of gas collected at 750 mm HG occupies 250. ml. At constant temperature, what pressure does the gas exert if the volume increases to 300 ml?
a. 50 mm Hg
b. 550. mm Hg
c. 625. mm Hg
d. 900. mm Hg
7. Conevert the pressure of 0.75 atm to mm Hg
a. 101.325 mm Hg
b. 760 mm Hg
c. 570 mm Hg
d. 430 mm Hg
8. The temperature of a sample of gas at 4.0 atm and 15 degrees C increases to 30 degrees C. If the volume is unchanged, what is the new gas pressure?
a. 4.2 atm
b. 3.8 atm
c. 19 atm
d. 8 atm
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Arkcon

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Re: General chemistry help with gases?
« Reply #1 on: March 01, 2009, 01:11:51 PM »

1. All of the following equations are statements of the ideal gas law except
A. R=PV/nT
B. PV/T=nR
C. P/n=RT/v
d. P=nRTV

OK.  Let's start with this one.  What is the usual form of the ideal gas law?  Can you get each of these from that one by rearranging algebraically?  Which one is wrong?

We like to help people to help themselves on this forum.  Dumping a long list of questions with no sign of effort on your part like you've just done is a little off-putting for the group.
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Nhockeyfreak

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Re: General chemistry help with gases?
« Reply #2 on: March 01, 2009, 01:13:48 PM »

PV=nRT
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Arkcon

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Re: General chemistry help with gases?
« Reply #3 on: March 01, 2009, 01:31:09 PM »

PV=nRT

A very good first step.  Now, algebra ...
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Nhockeyfreak

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Re: General chemistry help with gases?
« Reply #4 on: March 01, 2009, 01:31:18 PM »

C seems incorrect to me, but then again, so does A. just because A states that you can solve "r" which is amount of moles, and i thought that the gas equation was used to solve pressure and volume, not moles.
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Arkcon

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Re: General chemistry help with gases?
« Reply #5 on: March 01, 2009, 01:34:10 PM »

C seems incorrect to me, but then again, so does A. just because A states that you can solve "r" which is amount of moles, and i thought that the gas equation was used to solve pressure and volume, not moles.

No, we can rearrange the ideal gas law formula to solve for any one term, or ratio of terms, as needed.  You will need to do that, for question 5.
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Nhockeyfreak

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Re: General chemistry help with gases?
« Reply #6 on: March 01, 2009, 01:34:40 PM »

I know that to solve for p you use P= Nrt/v and to solve for T, you use T=pv/nr
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Nhockeyfreak

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Re: General chemistry help with gases?
« Reply #7 on: March 01, 2009, 01:40:35 PM »

the anwer has to be c because you cannot have pressure/ moles equal the gas constant times temperature/ volume.
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Arkcon

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Re: General chemistry help with gases?
« Reply #8 on: March 01, 2009, 01:41:52 PM »

I know that to solve for p you use P= Nrt/v and to solve for T, you use T=pv/nr

Can you see, how those are related algebraically to PV=nRT?  Oh, and do you now notice which of the multiple guess answers is wrong?

A couple of your questions are simple definitions.  It is hard for us to help you with a definition -- there really isn't a hint available for us to give you.  You can check your notes, read your book, use your book's index on keywords to save yourself some time, or just Goggle terms until you get lucky.  Us doing that for you really isn't helping you, it's just doing it for you.
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Borek

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Re: General chemistry help with gases?
« Reply #9 on: March 01, 2009, 08:43:46 PM »

the anwer has to be c because you cannot have pressure/ moles equal the gas constant times temperature/ volume.

Multiply both sides of the equation by nV.
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Nhockeyfreak

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Re: General chemistry help with gases?
« Reply #10 on: March 02, 2009, 03:21:21 AM »

I have concluded that the right answer for number 1 is D.
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Arkcon

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Re: General chemistry help with gases?
« Reply #11 on: March 02, 2009, 07:01:48 AM »

I have concluded that the right answer for number 1 is D.

Good.  Now, what would the correct one for P= be?  You should try to do things such as this, the instructor will not give you the exact same questions on the exam.  If you solved this one, then you should be ready to do question #5.  So how's that one working for you?
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Nhockeyfreak

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Re: General chemistry help with gases?
« Reply #12 on: March 02, 2009, 01:14:58 PM »

I am getting the hang of things. I am actually still in high school. But for number 5 I got B as my answer, and im pretty sure its corrrect. Btw I don't need any more help on these problems. I guess I just needed someone to give me a few pointers, because i dont see my teacher again till Wednesday. But thanks for the advice ..and P=nrt/v of course
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