Asked by jerson

for this question A sample of air has a volume of 140.0 mL at 67 degrees celcius. At what temperature would its volume 50.0 mL at constant pressure
I did
140.0 ml... 67+273=340
T2... 50.0
140.0=50.0
340=T2
340*50.0/140.0=121.4

This question i don't get because of the scientific notation. A sample of oxygen that occupies 1.00 x 10^6 mL at 575 mm Hg is subjected to a pressure of 1.25 atm. What will the final volume of the sample be if the temp is held constant?
Answered by DrBob222
The first one is ok EXCEPT that if your prof is a stickler for significant figures, you will get points counted off if not the entire question. The smallest number of significant figures is 3 (50.0, 340) so the most s.f. you are allowed in the answer is 3; therefore, you would round the answer to 121. ALSO, some profs will count off if you don't have units; therefore, the complete answer would be 121 Kelvin.
For the second problem, 10^6 just means to add 6 zeros to 1 (which would be 1,000,000). Or you can key in the number with scientific notation to your calculator and let it keep track of the decimal. USUALLY, a number expressed as 1.00 x 10^6 mL means your prof looks at s.f.
Answered by jerson
ok i get that now.. but now im still confused with how to solve the problem because i don't see where it talks about temperature.
Answered by DrBob222
Sure. It says the temperature is held constant. This is a pressure/volume problem. Done the same way except
P1V1 = P2V2.

By the way, do you know how to keep all these formulas straight? Do it this way.
The general formula is
(P1V1)/T1 = (P2V2)/T2
If T is constant, just cover up T1 and T2 with your fingers (or mentally) and you have P1V1 = P2V2 which is Boyle's Law.
If P is held constant, cover up P1 and P2 with your fingers (or mentally), and you have V1/T1 = V2/T2 which is Charles' Law.
If V is held constant, covert up V1 and V2 with yur fingers (or mentally) and you have P1/T1 = P2/V2. Easy, huh?
You only need to memorize the general formula that contains all the variable and tailor it to fit the problem. And, of course, you must remember that T always goes in with Kelvin.
Answered by DrBob222
<b>If V is held constant, covert up V1 and V2 with yur fingers (or mentally) and you have P1/T1 = P2/V2. Easy, huh? </b>

<i>I made a goof here. This should read, if V is held constant, cover up V1 and V2 with your fingers (or mentally) and you have P1/T1 = P2/T2
My fingers sometimes get ahead of my brain.</i>
Answered by jerson
well im sure u can tell chemistry is my weakest subject because im still confused :/...

so would it be 1000000= 575
1.25= t2?
Answered by DrBob222
Why do you want to solve for t? It SAYS t is constant so we don't care what it is. And you haven't used the pressure at all.
You didn't do what I said. Just follow the guide lines.
P1V1/T1 = P2V2/T2.
Now, since T is constant, cover T1 and T2 with your fingers, or mentally, and we are left with
P1V1 = P2V2
Now look at the problem.
V1 = 1 x 10^6 mL
P1 = 575 mm Hg
V2 = ?? mL.
P2 = 1.25 atm.
Right away you see that the units on pressure don't match. You must change mm Hg to atmospheres OR change atmospheres to mm Hg. The conversion factor is 760 mm = 1 atm. The easy one to change is P1 so 575/760 = 0.756 atm.
Then P1V1 = P2V2
0.756*1x10^6 = 1.25*V2 and solve for V2.
Answered by jerson
ok thank you for all of your help tonight.. i really appreciate it!
Answered by DrBob222
You're welcome.
Answered by Anonymous
p1v1/t1=p2vp/t2;v2
There are no AI answers yet. The ability to request AI answers is coming soon!