Module 4.4 Gas Laws

Question 1

What do the letters represent

PV = n R T

Answer 1

P= Pressure
V= Volume
n= Number of moles
R= always have value of 0.0821
T= Temperature

Question 2

What are the units for each letter

PV = n R T

Answer 2

P= atm (atmospheres) if not in atm form the take the mm / 760 to get atm 
V= l (liters) if not in l (liters) take the ml / 1000 to get l (liters) 
n= moles
R= 0.0821
T= °K in not in °K take the °C +273 to get °K

Question 3

CO₂ 8.8g 1520mm 27°C

Answer 3

First set up formula PV = n R T

(1520mm) (V) = (n) (0.0821) (27°C)

Convert all to the correct units 
1520mm/760 = 2atm
27°C + 273 = 300°K
CO₂ = C=12*1=12 + O=16*2=32 = 44MW
8.8g / 44MW = 0.20moles

(2atm) (V) = (0.20) (0.0821) (300°k)

Divide left side of = sign to separate V

V = (0.20) (0.0821) (300°k) / 2

V = (4.926) / 2 = V = 2.463l (liters)

Question 4

PᵢVᵢ P𝒻V𝒻
—— = ———
Tᵢ T𝒻

Gas
500ml 380mm -173°C ——> V? 760mm 27°C

Answer 4

Convert to the correct units

(initial gas)
500ml /1000 = 0.5l
380mm/760= 0.5atm
-173°C + 273 = 100°K

final gas
v= ?
760mm/760= 1atm
27°C + 273 = 300°K

(0.5) (0.5) (1) (V𝒻)
————— = ————
(100°K) (300°K)

Cross multiply numerator & denominator

100 * 1 * V𝒻 = 100V𝒻
(0.5) * (0.5) * (300) = 75

100V𝒻 = 75

divid both sides of = sign by 100 to separate V𝒻

V𝒻 = 0.75