# Gas pressure

1. Sep 29, 2009

### ibysaiyan

1. The problem statement, all variables and given/known data
An Aerosol has a of pressure 250kpa at 17 C.The aerosol is left in the sun and its temp.rises to 27 C.Calculate new pressure in the can if its a 35% increase in the amount of vapour present.

2. Relevant equations
P/T= constant

3. The attempt at a solution
well tbh i am just confused.. do i get T= into kelvin, ok i tried that too...
my first attemp was:
1)(273.15+27)-(17+273.15)=10kelvin
so what i did:10x250x10^3/100= 25kPa
so pressure at 27 is: 250+25=275Kpa
2)
2nd attempt:
PV=nRT
P/T=nr/v
=>P/T= constant
250x10^3/10kelvin=25kpa... which if i add to 250 gives me same answer.. lol i have confused my self badly -(. first i forgot to convert C into Kelvin .
Thanks for the replies in adv.

2. Sep 29, 2009

### RoyalCat

Try and work in an ordered way. Always try and structure your work in advance. Write out what you know, and what you're looking for.

And I think you shouldn't work with $$P/T=constant$$
That's just a misleading way of saying that the volume is constant, and I think it can only lead to confusion.

Initial state:

$$P_1 V_1 = nRT_1$$

$$P_1= 250kPa$$

$$V_1=V_2$$ (As long as the can doesn't deform, its total volume remains the same)

$$T_1=(17+273.15) ^o K$$

Final state:

$$P_2 V_2 = nRT_2$$

We are looking for $$P_2$$

$$V_2=V_1$$

$$T_2=(27+273.15) ^o K$$

Now all that you need to do is isolate $$P_2$$ and express it in terms of known quantities.

Last edited: Sep 29, 2009
3. Sep 29, 2009

### ibysaiyan

ermm sorry i dont get it , do you mean that i should isolate p2 =nRT2/v2

4. Sep 29, 2009

### RoyalCat

Yes...
Now find a way to express $$V_2$$ in terms of known quantities.