Worksheet: Graham’s Law

In this worksheet, we will practice using Graham’s law to calculate the relative effusion rates of gases from the square roots of the molar masses.

Q1:

An unknown hydrocarbon gas effuses 1.66 times more rapidly than CO2.

What is the molar mass of the unknown gas? Give your answer to 1 decimal place.

What is the likely identity of the gas?

  • ACH36
  • BCH22
  • CCH4
  • DCH26
  • ECH24

Q2:

Which of the following gases diffuses faster than oxygen?

  • AHS2
  • BNO2
  • CCH22
  • DCl2
  • EF2

Q3:

A balloon filled with helium gas is found to take 6.00 hours to deflate to 50% of its original volume. How long will it take for an identical balloon filled with the same volume of hydrogen gas (instead of helium) to decrease its volume by 50%?

Q4:

When two cotton plugs, one moistened with ammonia and the other with hydrochloric acid, are simultaneously inserted into opposite ends of a glass tube that is 87.0 cm long, a white ring of NHCl4 forms where gaseous NH3 and gaseous HCl first come into contact. Ammonia and hydrochloric acid react together according to the equation shown. NH()+HCl()NHCl()34ggs

How far from the end with ammonia would you expect the ring to form?

Q5:

It takes 243 s for 4.46×10 molXe to effuse through a tiny hole. Under the same conditions, how long will it take 4.46×10 molNe to effuse?

Q6:

What is the ratio of the rate of effusion of hydrogen to the rate of effusion of oxygen?

  • A21
  • B32
  • C43
  • D41
  • E14

Q7:

An equal number of moles of fluorine and helium diffuse into a chamber with no change in pressure or temperature. Calculate to 2 significant figures the diffusion rate of fluorine as a percentage of the diffusion rate of helium?

Q8:

An equal number of moles of nitrogen and a second gas diffuse into a chamber with no change in pressure or temperature. What is the molar mass of the second gas to the nearest gram per mole if its diffusion rate is two-thirds less than that of nitrogen?

Q9:

An equal number of moles of argon and a second gas diffuse into a chamber with no change in pressure or temperature. What is the molar mass of the second gas to the nearest gram per mole if its diffusion rate is 41%‎ greater than that of argon?

Q10:

An equal number of moles of neon-20 and a second gas diffuse into a chamber with no change in pressure or temperature. Which of the following is a possible molecular formula for the second gas if its diffusion rate is 56.2% lower than that of neon-20?

  • ACHS26
  • BHBrO
  • CSiF4
  • DNO2
  • EHCl

Q11:

An equal number of moles of oxygen and hydrogen gas diffuse into a chamber with no change in pressure or temperature. By approximately what factor does the diffusion rate of oxygen differ from that of hydrogen?

  • A18
  • B116
  • C132
  • D18
  • E14

Q12:

The molecules in gas A have molecular mass 𝑀A and an average speed 𝑣A, while the molecules in gas B have molecular mass 𝑀B and an average speed 𝑣B.

If the gases are at the same temperature, how may the ratio 𝑣/𝑣AB be expressed in terms of 𝑀A and 𝑀B?

  • A𝑀𝑀AB
  • B𝑀𝑀BA
  • C𝑀𝑀AB
  • D𝑀𝑀AB
  • E𝑀𝑀BA

If the temperature of gas A is doubled and the temperature of gas B remains constant, by what factor does the ratio 𝑣/𝑣AB increase?

  • A12
  • B12
  • C4
  • D2
  • E2

Q13:

Two bulbs, one containing helium and one containing argon, are connected by a tube. A valve in the tube separates the two gases.

What will happen when the valve is opened?

  • AThe gases will mix, but there will be a helium-rich bulb and an argon-rich bulb.
  • BThe two gases will mix until completely homogeneous.
  • CThe gases will remain in their bulbs, as there is no energy driving them to mix.

If the valve is opened and the gases mix together, which of these statements is false?

  • AThe total energy of the system will increase.
  • BThe total enthalpy of the system will remain unchanged.
  • CThe disorder in the system will increase.
  • DThe total entropy of the system will increase.

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