Solve using Gas Law.a gven mass of gas occupies a 200ml.a 700 mm.Hg & 20degC.compune for the vol of gas at STP

Question

its 20 degrees celsius...the space is not enough..pls help me..thank you in advance

Answer 1

This is a combined gas law problem.  (Tip off: The question deals with one gas sample whose parameters change somehow.  You can call this a "before and after" kind of problem.)

(P1V1)/T1 = (P2V2)/ T2

What is "1" and what is "2" is arbitrary, as long as you are consistent about it. So for now, I'll say that the "before" is "1" and the "after" is "2".

P1 = 700 mmHg

V1 = 200 mL

T1 = 20 deg C (convert to K)

(remember STP?  760 mmHg and 273K (or 1 atm and 0 deg C).  Plug that in as your "after" numbers.)

P2 = 760 mmHg

V2 = ?

T2 = 273 K

** Note: The combined gas law is not as fussy about units as the ideal gas law.  You do NOT need to convert mmHg to atm or kPa, or mL to L.  One way to think about this is that the ideal gas law has a constant in there that is highly dependent on the units you have.  The only exception to this unit conversion thing is the temperature.  The temperature MUST be in Kelvin.

So, let's do this.

Step 1: Clean up your numbers (i.e., convert your numbers)

P1 = 700 mmHg

V1 = 200 mL

T1 = 20 deg C = 293K

P2 = 760 mmHg

V2 = ?

T2 = 273 K

Step 2: Clean up the equation.

(P1V1)/T1 = (P2V2)/ T2

(P1 V1 T2) / (T1 P2) = V2

Step 3: Plug and solve.

(700 mmHg * 200 mL * 273K) / (293K * 760 mmHg) = V2

172 mL = V2

(3 sig figs here for the sake of clarity.  Looks like this is going to be an answer with only 1 SF in it, given the way the numbers are typed.)

Answer 2

Could you please rewrite the question - don't be afraid to take some time.  I can barely read the question you wrote.  Take pride in your work!!

Sincerley,

G.C.

P.S.  If you do, I'll help you out.

Answer 3

T = °C + 273 = K: STP = 1atm (760mmHg) and 273K).

Combined Gas Law. P1 x V1 x T2 = P2 x V2 x T1.

P1, V1, T1 are the Initial parameters.

P2, V2 , T2 are the Final parameters.

700mmHg x 200mL x 273K = 760mmHg x V2 x 293K.

V2 at STP = (700 x 200 x 273) / (760 x 293).

= 38,220,000 / 222,680 = 171.6mL.