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In this lesson, we will learn how to use Graham's law to calculate the relative effusion rates of gases from the square roots of the molar masses.

Q1:

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 N H C l 4 forms where gaseous N H 3 and gaseous H C l first come into contact. Ammonia and hydrochloric acid react together according to the equation

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

Q2:

A balloon filled with helium gas is found to take 6.00 hours to deflate to 5 0 % 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 5 0 % ?

Q3:

It takes 243 s for 4 . 4 6 × 1 0 mol X e to effuse through a tiny hole. Under the same conditions, how long will it take 4 . 4 6 × 1 0 mol N e to effuse?

Q4:

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 5 6 . 2 % lower than that of neon-20?

Q5:

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?

Q6:

An unknown hydrocarbon gas effuses 1.66 times more rapidly than C O 2 .

What is the molar mass of the unknown gas?

What is the likely identity of the gas?

Q7:

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 g/mol if its diffusion rate is 4 1 % greater than that of argon?

Q8:

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

Q9:

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 g/mol if its diffusion rate is two thirds less than that of nitrogen?

Q10:

Which of the following gases diffuses faster than oxygen?

Q11:

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?

Q12:

The molecules in gas A have molecular mass 𝑀 A and an average speed 𝑣 A , while the molecules in gas B have molecular mass 𝑀 B and an average speed 𝑣 B .

If the gases are at the same temperature, how may the ratio 𝑣 / 𝑣 A B be expressed in terms of 𝑀 A and 𝑀 B ?

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

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