Homework Help: Physics Homework Help Please

1. Feb 12, 2012

geek2012

1. A sample of neon gas has its volume tripled and its temperature held constant. What will be the new pressure relative to the initial pressure?

2. A fire breaks out and increases the Kelvin temperature of a cylinder of compressed gas by a factor of 3.0. What is the final pressure of the gas relative to its initial pressure?

3. If a quantity of gas in a piston cylinder has a volume of 0.501 m3 and is initially at room temperature (20°C) and is heated in an isobaric (constant-pressure) process, what will be the temperature of the gas in degrees Celsius when it has expanded to a volume of 0.706 m3?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 12, 2012

DaveC426913

We do not spoonfeed homework here. You must show your attempts at a solution before anyone can help you.

It is in the rules that you read when you signed up.

These are basic applications of the Gas Laws. Look them up in your book to see which ones apply.

3. Feb 12, 2012

geek2012

Well, let's start with this one.....A sample of neon gas has its volume tripled and its temperature held constant. What will be the new pressure relative to the initial pressure?

I don't even know where to begin because I don't have the amount of neon gas, the original temp or volume, so I don't know how to even plug it in the equation....i know it's p1/p2=(t2/t1)(v1/v2)

4. Feb 12, 2012

DaveC426913

What law is applicable? Look at what variable(s) you are given and what you are trying to solve for.

You are not being asked for numbers, you are being asked for a final value relative to the initial value. i.e. algebraically. If v2 triples, what happens to p2?

5. Feb 12, 2012

geek2012

well the 1st law is finding heat, so I dont need that one. the second law is inability for heat to flow from cold to hot body, and the third law of thermodynamics says that it is impossible to get a temp of absolute zero, but i dont know what my temp is. I don't know which one is applicable.

I'm a total beginner to this stuff. I apologize. I could really use all the help I can get.

6. Feb 12, 2012

geek2012

if v2 triples, then wouldn't the p2 triple as well?

7. Feb 12, 2012

DaveC426913

(You're looking at the laws of thermodynamics. You need to be looking at the Gas Laws. http://en.wikipedia.org/wiki/Gas_laws)

Last edited: Feb 12, 2012
8. Feb 12, 2012

DaveC426913

9. Feb 12, 2012

geek2012

okay, so using that formula, how would I go about solving it?

p1/p2=(t2/t1)(v1/v2)

I'm solving for p1/p2....so my t2/t1 would be ?? I don't have a temp...

and volume is tripled but I don't have an intial volume...

I figured that if v2 is tripled, then p2 would be tripled as well, I entered in 3 as the answer, but it was wrong.

10. Feb 12, 2012

DaveC426913

1] Temp doesn't change. That means t1=t2. Unless t is zero, t1/t2 will always equal 1. If it's 1 then it drops out of the equation. Do you see why intuitively? If a property doesn't change between time a and time b, then that property is not involved in the equation. So drop it.

11. Feb 12, 2012

geek2012

so it would now be p1/p2=v1/v2 ??

12. Feb 12, 2012

DaveC426913

Wait a minute. I wasn't paying attention. Where did you get that formula?

Does your book cover Boyle's Law and Charles' Law and the other gas laws?

13. Feb 12, 2012

geek2012

it was p1/p2=(t2/t1)(v1/v2).
you told me that if a property doesn't change, it equals one and drops out of the equation, so that would leave me p1/p2=v1/v2, correct?

14. Feb 12, 2012

DaveC426913

Where did you get this formula?

15. Feb 12, 2012

geek2012

oops...sorry... p2/p1=v1/v2

is that right?

16. Feb 12, 2012

DaveC426913

It is usually expressed as v1*p1 = v2*p2, but yours will work.

So, what happens to p2 if v2 is triple the value of v1?

Start with your formula. For all initial values, use 1. You're given v2, so what's p2 going to have to be? Show your work.

Last edited: Feb 12, 2012
17. Feb 12, 2012

geek2012

so boyle's law has that equation you had....the v1*p1=v2*p2, and if you triple v2, then it would triple the intial pressure. is that right?

18. Feb 12, 2012

DaveC426913

Stop guessing and show your work.

Assume initial values p and v are 1. You're given v2.

19. Feb 12, 2012

geek2012

i don't know how to even begin to show my work.

you said v1*p1=v2*p2

if v2 is triple of v1, then p2 is triple of p1...so, I'm going to make a wild guess here...

v1*p1=3*3

I put 3 times 3, because it's tripled on each one. If this isn't correct, then I have no idea what to do. LOL

20. Feb 12, 2012

DaveC426913

What grade are you in? Do you know how to write out and solve an equation?

v1*p1=v2*p2

So

(1)*(1)=(3)*p2

What must p2 be for the left side to equal the right side?

p2=...