[Mr.2007]

The Question is

What is the Temperature of 3.60 mole nitrogen gas that is contained in a 300.0ml flask at 15.8 atm

do i use pv=nRT

if i do how do i rearrange it to solve for temp

[Yggdrasil]

Yes, you use PV=nRT.

To solve for temperature, divide both sides of the equation by nR.

[Mr.2007]

So it would be

T = PV
      NR

[Yggdrasil]

Yes.

[Mr.2007]

alight Ygg can you help me with this problem

A helium filled balloon has a volume of 250mL at 50^oC and 100atm at what temperature would the balloon occupy 87mL at 200atm

i know i use

P₁*V₁ = P₂*V₂
   T₁        T₂

but how do i rearrange it to solve for temp

[enahs]

You can work the helium one several ways.

You can use the conditions you are first given (Volume, pressure, temp) and solve for n with your standard PV = nRT. Since it is a closed system, the n is the same, and so you can plug in your new pressure and volume (along with n) in PV = nRT and solve for T (which is just like the first question).


For the math question you asked

P1*V1 = P2*V2
   T1        T2

but how do i rearrange it to solve for temp

You are solving for T₂, so first multiply both sides by T₂. Then divide both sides by  (P₁*V₁)/T₁

[Mr.2007]

^^^^^

I already worked like this don't know if its right

T1 * P1 * V1 = T2
    P2 * V2

[enahs]

^^^^^

I already worked like this don't know if its right

T1 * P1 * V1 = T2
    P2 * V2

No, it is not right.

You need to study up on your basic algebra (it is very useful and you will use it a lot the rest of your life, do not fight it!)
http://www.intmath.com/Basic-algebra/Basic-algebra-intro.php
http://library.thinkquest.org/20991/prealg/eq.html
http://www.mathleague.com/help/algebra/algebra.htm

[Mr.2007]

You can work the helium one several ways.

You can use the conditions you are first given (Volume, pressure, temp) and solve for n with your standard PV = nRT. Since it is a closed system, the n is the same, and so you can plug in your new pressure and volume (along with n) in PV = nRT and solve for T (which is just like the first question).


 For the math question you asked

P1*V1 = P2*V2
   T1        T2

but how do i rearrange it to solve for temp

You are solving for T₂, so first multiply both sides by T₂. Then divide both sides by  (P₁*V₁)/T₁

did you mean multiply both sides by T1 because I'm solving for T2

but i worked it the first way you said to

N = PV
      RT

Then I did

T = PV
      NR
I converted 25ml t0 .25L and 50^oC to 323K

and i got .0000208

can you work the problem and see if thats right and give me the combined gas law formula to solve for temp.

[Mr.2007]

^^^^

I just thought about this, I think its wrong because I didn't use the 87ml or 200atm

[Mr.2007]

alright i re did with the 87mL which i converted to .87L and the 200atm and i got .0001452 can you work it and see if thats right

[enahs]

First, solving for n at given conditions.

P₁ * V₁ = n₁*R*T₁

n = P₁ * V₁
      R * T₁

n = 100 atm * 0.25 L
   8.206 x 10^-2 L atm K^-1 mol^-1 * 323.15 K

n= 0.942_7669206


Now, using that n to solve for T at the second conditions.

P₂ * V₂ = n * R * T₂

T₂ = P₂ * V₂
        n * R


T₂ =  200 atm * 0.087 L
       0.942 mol * 8.206 x 10^-2 L atm K^-1 mol^-1

T₂ = 224.9₁₂₄ K





Algebra, step by step (not the fastest or easiest way,but I purposely do that so you can see the basics of algebra applied multipul times):

P₁ * V₁  =   P₂ * V₂
    T₁              T₂

First, multiplying both sides by T₂

P₁ * V₁  * T₂ =   P₂ * V₂ * T₂
    T₁                     T₂

Which is

P₁ * V₁ * T₂ = P₂ * V₂
       T₁

Multiply both sides by T₁

P₁ * V₁ * T₂  * T₁ = P₂ * V₂ * T₁
      T₁

Which is

P₁ * V₁ * T₂ = P₂ * V₂ * T₁

Now, divide both sides by P₁ * V₁


P₁ * V₁  * T₂ = P₂ * V₂ * T₁
P₁ * V₁               P₁ * V₁

Which is
T₂ = P₂ * V₂ * T₁
           P₁ * V₁

T₂ = 200 atm * 0.087 L * 323.15 K
           100 atm * 0.25 L

T₂= 224.9₁₂₄ K

Notice how your units cancel, leaving you with just K on both sides.

T₂ (K) = 200 atm * 0.087 L * 323.15 K
           100 atm * 0.25 L


Conversely, the same thing is done (much faster) if you first invert both side:
That is,

P₁ * V₁  =   P₂ * V₂
    T₁              T₂

Goes to.
    T₁         =      T₂ 
P₁ * V₁            P₂ * V₂

And then you just have to multiply both sides my P₂ * V₂.



Both ways have on thing in common, you can do anything you want to it, as long as you do it to both sides. This is just algebra, take some time and and study your algebra book, or check out those sites I linked you. This is some very basic algebra, you need to get the hang of it.

[Mr.2007]

^^^

Thanks for all your help enahs