1. A sample of N2O gas has a density of 2.75 g/L at 298 K A) What must be the pr

Question

1. A sample of N2O gas has a density of 2.75 g/L at 298 K

A) What must be the pressure of the gas Hg?

2. An experiment shows that a 115 mL gas sample has a mass of 0.172 g at a pressure of 723 Hg and a temperature of 34 { m ^circ C} .

B) What is the molar mass of the gas?

3. A gas mixture with a total pressure of 770 Hg contains each of the following gases at the indicated partial pressures: 124 Hg CO2 , 228 Hg Ar , and 187 Hg O2 . The mixture also contains helium gas.

C) What is the partial pressure of the helium gas?

Explanation / Answer

1. Density of N2O = 2.75 g/L

Temperature = 298 K

Volume of N2O = 1 L

mass of N2O = 2.75 g

Moles of N2O = 2.75 / 44.013

= 0.0624

Using PV = nRT

P = 0.0624 * 0.0821 * 298 / 1

= 1.526 atm

2. Volume of gas sample = 115 mL = 0.115 L

Pressure = 723 mmHg = 0.9513 atm

Temperature = 34 oC = 307.15 K

PV = nRT

0.9513*0.115 = n*0.0821*307.15

0.109 = n * 25.21

n = 0.00432

Mass of gas = 0.172 g

Molar mass = Mass / Moles

= 0.172 / 0.00432

= 39.81 g/mol

3. Total pressure = 770 mmHg

partial pressure of CO2 = 124 mmHg

partial pressure of Ar = 228 mmHg

partial pressure of O2 = 187 mmHg

we know that,

p1 + p2 + p3 + p3 = Total pressure

124 + 228 + 187 + p4 = 770

539 + p4 = 770

p4 = 231 mmHg

So, partial pressure of Helium = 231 mmHg

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