1. Assuming constant pressure. What will the volume of gas be at -12 degrees cel

Question

1. Assuming constant pressure. What will the volume of gas be at -12 degrees celsius, when the balloon started at 250 mL at 25 degrees celsius?

2. Assuning constant temperature. What will be the volume of gas, when 250 mL of gas at 650mm HG, is placed in a vacuum and the pressure reduced to 0.25 atm?

3. What will the volume of helium be at STP when initially the volume of helium is 35 mL at 35 degrees celsius and 700 mm Hg?

4. What will be the volume of 6.5 grams of helium at -10 degrees celcius and 680 mm Hg.

5. Determine the density of sulfur dioxide at STP in g/L.

Explanation / Answer

1.
When pressure is constant,
use:
V1/T1 =V2/T2

Here:
V1 = 250 mL
T1 = 25 oC = (25+273)K =298 K
V2=?
T2= - 12oC = (-12+273)K= 261 K

use:
V1/T1 =V2/T2
250/298 = V2/261
V2=219 mL
Answer: 219 mL

2.
when T is constant use:
P1*V1 = P2*V2

P1 = 650 mm Hg = 650/760 atm=0.86 atm
V1=250 mL
P2=0.25 atm
V2=?

P1*V1 = P2*V2
0.86 * 250 = 0.25*V2
V2=855.3 mL
Answer: 855.3 mL

3.
use:
P1*V1/T1=P2*V2/T2
700*35/(35+273) = 760*V2/273
V2=28.6 mL

4.
Use:
P*V=n*R*T

P=700 mm Hg = 680/760 atm =0.895 atm
V =?
n=mass/molar mass = 6.5/4=1.625 mol
T=(-10 + 273) K = 263 K

Use:
P*V=n*R*T
0.895*V = 1.625*0.0821*263
V= 39.2 L

5.
AT STP,
22.4 L contains 1 mol
mass of 1 mol SO2 = 64 g

density = mass / volume
     = 64 g / 22.4 L
     =2.86 g/L

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