Diffusion

Two gas jars are arranged as shown. The lid is taken off and the gas jars are left standing. After a while, the contents of both gas jars turn brown. Which process makes this happen?

Feb/March 2016

Two gas jars are arranged as shown. The lid is removed and the gas jars are left to stand. After some time, the contents of both gas jars are brown. Which process causes this to happen?

Feb/March 2016

A bottle containing aqueous ammonia is left on a table in one corner of the laboratory. The stopper is taken out and, after a few minutes, every student in the room is able to detect the smell of ammonia. Which process takes place?

Feb/March 2017

Hydrogen chloride gas, $\text{HCl}$, reacts with ammonia gas, $\text{NH}_3$, to produce solid ammonium chloride. The apparatus is arranged as shown. After a few minutes, solid ammonium chloride appears at the point where the two gases meet. The experiment is repeated with hydrogen bromide, $\text{HBr}$, used instead of hydrogen chloride. At what distance along the tube does solid ammonium bromide form?

Feb/March 2018

The formula for methane is $\text{CH}_4$ and the formula for ethane is $\text{C}_2\text{H}_6$. Which row gives the definition of diffusion and compares the relative rates of diffusion for methane and ethane?

Feb/March 2020

The substances listed below are gases at room temperature and pressure. hydrogen nitrogen oxygen chlorine

Feb/March 2021

Which gas diffuses at the fastest rate?

Feb/March 2023

Which of the following statements about diffusion are correct? 1. Aqueous ions are unable to diffuse in water. 2. Diffusion happens because particles move randomly. 3. During diffusion, particles spread out in every direction. 4. Diffusion can occur only in solids and liquids.

Feb/March 2024

Four samples of gases are let out into a room at the same time. The gases are carbon dioxide, $\text{CO}_2$, hydrogen chloride, $\text{HCl}$, hydrogen sulfide, $\text{H}_2\text{S}$, and nitrogen dioxide, $\text{NO}_2$. Which gas diffuses the most rapidly?

Feb/March 2025

The rate at which two gases, methane, $\text{CH}_4$, and ethene, $\text{C}_2\text{H}_4$, diffuse is being investigated with the apparatus shown. Which gas diffuses more quickly, and why?

May/June 2016

The diagram illustrates an experiment used to demonstrate diffusion. Which statement explains why the ammonium chloride ring is seen in the position shown?

May/June 2016

Concentrated ammonia solution releases ammonia gas, while concentrated hydrochloric acid releases hydrogen chloride gas. Ammonia, NH$_3$, and hydrogen chloride, HCl, are both colourless gases. When ammonia reacts with hydrogen chloride, the white solid ammonium chloride is produced. The apparatus is arranged as shown, with cotton wool soaked in concentrated hydrochloric acid at one end of a glass tube and cotton wool soaked in concentrated ammonia solution at the other end. Points A, B, C and D are marked along the tube. After ten minutes, a white solid appears in the tube where the two gases meet.

May/June 2016

Tiny crystals of purple $ ext{KMnO}_4$ ($M_r = 158$) and orange $ ext{K}_2 ext{Cr}_2 ext{O}_7$ ($M_r = 294$) were each placed at the centre of separate petri dishes that had been filled with agar jelly. They were then left in the same set of physical conditions. After a period of time, the colour of each substance had diffused outward as shown. The arrows show the relative distances moved by particles of each substance. Which of the following statements is correct?

May/June 2017

Tiny crystals of purple $\text{KMnO}_4$ ($M_r = 158$) and orange $\text{K}_2\text{Cr}_2\text{O}_7$ ($M_r = 294$) were put at the centres of separate petri dishes containing agar jelly. They were then left under identical physical conditions. After a period of time, the colour from each substance had spread out as shown. The arrow lengths show the comparative distances moved by particles of each substance. Which statement is correct?

May/June 2017

Small crystals of purple $\text{KMnO}_4$ ($M_r = 158$) and orange $\text{K}_2\text{Cr}_2\text{O}_7$ ($M_r = 294$) were each placed at the middle of separate petri dishes containing agar jelly. They were then left in the same conditions. After a period of time, the colour of each substance had spread out, as shown. The arrow lengths show the relative distances moved by particles of each substance. Which statement is correct?

May/June 2017

Mineral wool that has been soaked in aqueous ammonia is put into the apparatus illustrated. Five minutes later, the moist red litmus paper changed to blue. Which process caused this colour change?

May/June 2018

A student carried out an investigation into the diffusion of ammonia gas, $\text{NH}_3$, and hydrogen chloride gas, $\text{HCl}$. At room temperature and pressure, two sets of apparatus were arranged as shown. In apparatus 1, the damp red litmus paper changed colour after $30$ seconds. How long does the damp blue litmus paper take to change colour in apparatus 2?

May/June 2018

Ammonia gas is allowed to react with hydrogen chloride gas in the apparatus illustrated. Solid ammonium chloride forms. Which statement accounts for the solid ammonium chloride being produced closer to the hydrogen chloride?

May/June 2018

Which statement gives the reason why ammonia gas, $\text{NH}_3$, diffuses more quickly than hydrogen chloride gas, $\text{HCl}$?

May/June 2019

The apparatus illustrated has been assembled. After 20 minutes, a white ring of ammonium chloride appears at position Y. Which statement concerning the molecules of ammonia and hydrogen chloride is correct?

May/June 2019

Hydrogen chloride gas ($M_r = 36.5$) is given off at P in the apparatus illustrated. The Universal Indicator paper becomes red after 38 s. The experiment is carried out again with sulfur dioxide ($M_r = 64$). What happens with sulfur dioxide?

May/June 2019

Under appropriate temperature and pressure conditions, solid carbon dioxide passes straight into the gaseous state. Carbon dioxide gas diffuses from an area of higher concentration to an area of lower concentration. Which row gives the names of these two processes?

May/June 2021

At the same temperature, which two gases diffuse at the same rate?

May/June 2022

At the same temperature, which two gases diffuse at the same rate?

May/June 2022

At an identical temperature, which two gases will diffuse at identical rates?

May/June 2022

The diagram illustrates what happens when a purple crystal is placed into water. Which processes occur in this experiment?

May/June 2023

The diagram illustrates what happens when a purple crystal is placed in water. Which processes occur in this experiment?

May/June 2023

Hydrogen chloride gas ($M_r$: HCl, $36.5$) is released at P in the apparatus illustrated. The universal indicator paper changes to red after $38\,\text{s}$. The experiment is carried out again using sulfur dioxide gas ($M_r$: $\text{SO}_2$, $64$). What outcome is obtained for sulfur dioxide gas?

May/June 2024

Which gas diffuses at the slowest rate?

May/June 2024

When hydrogen chloride gas, $\text{HCl}$, comes into contact with ammonia gas, $\text{NH}_3$, solid ammonium chloride is produced. The experiment is then carried out again, but hydrogen bromide gas, $\text{HBr}$, is used instead of hydrogen chloride. At what point along the tube does the white cloud of solid ammonium bromide appear?

May/June 2024

Nitrogen dioxide is a red-brown gas that is denser than air. The diagram illustrates the setup of two gas jars containing nitrogen dioxide and air, with a glass plate between them. The glass plate is taken away, and the gas jars are left for $24$ hours. Which diagram shows the gas jars after $24$ hours?

May/June 2025

‘Particles moving at a very slow rate from a region of higher concentration into a region of lower concentration.’ Which process is being described?

Oct/Nov 2016

'Particles travelling at a low rate from a region of higher concentration to a region of lower concentration.' Which process is described here?

Oct/Nov 2016

‘Particles passing very slowly from a region of higher concentration to a region of lower concentration.’ Which process is being described?

Oct/Nov 2016

‘Particles that move very slowly from a region of higher concentration to a region of lower concentration.’ Which process is this describing?

Oct/Nov 2016

‘Particles moving very slowly from a region of higher concentration to a region of lower concentration.’ Which process is being described?

Oct/Nov 2016

‘Particles travelling at a very slow rate from a region of higher concentration to a region of lower concentration.’ Which process does this description refer to?

Oct/Nov 2016

Tiny holes in the walls of a porous pot let gases pass into or out of the pot. A teacher filled a porous pot with green chlorine gas, then put the pot inside a large jar of air. After 10 minutes, a green colour was observed outside the porous pot.

Oct/Nov 2016

A few drops of liquid bromine were put at the bottom of a beaker containing cyclohexane. After 3 days, a red-brown colour had spread through the entire beaker. Explain these observations using the kinetic particle model.

Oct/Nov 2017

Which term is used for the random movement of the dust particles?

Oct/Nov 2017

Carbon and silicon are elements in Group IV of the Periodic Table. Carbon dioxide in the air enters green plants and is changed into carbohydrates.

Oct/Nov 2017

If smoke particles are viewed through a microscope, they can be seen wandering about in an irregular way. This is known as Brownian motion. What is responsible for Brownian motion?

Oct/Nov 2018

Oxygen and fluorine are gaseous elements that are adjacent in the Periodic Table. When both are under the same temperature and pressure conditions, oxygen diffuses ......1...... more slowly than fluorine because its ......2...... is lower than fluorine's. Which words correctly fill gaps 1 and 2?

Oct/Nov 2018

The apparatus illustrated is assembled and then left for one week. Which diagram indicates the water level at the end of the week?

Oct/Nov 2019

The apparatus illustrated is assembled and then left for a week. Which diagram shows the water level at the end of the week?

Oct/Nov 2019

The apparatus illustrated is arranged and then left for a week. Which diagram shows the water level at the end of the week?

Oct/Nov 2019

At the same moment, four gas samples are let out into a room. Those gases are carbon dioxide, $\text{CO}_2$, hydrogen chloride, $\text{HCl}$, hydrogen sulfide, $\text{H}_2\text{S}$, and nitrogen dioxide, $\text{NO}_2$. Which gas has the greatest rate of diffusion?

Oct/Nov 2019

The apparatus illustrated is assembled and then left for one week. Which diagram represents the water level after the week has ended?

Oct/Nov 2019

The speed at which a gas diffuses is affected by its molecular mass and temperature. Which pairing of molecular mass and temperature produces the slowest diffusion rate?

Oct/Nov 2019

At the same temperature, which two gases diffuse at the same rate?

Oct/Nov 2019

The apparatus illustrated is assembled and then left for a week. Which diagram indicates the water level at the end of the week?

Oct/Nov 2019

The gradual movement of a substance from a region of high concentration to one of low concentration. Which process is described here?

Oct/Nov 2020

‘The gradual spreading of a substance from a region of higher concentration to a region of lower concentration.’ Which process is being described?

Oct/Nov 2020

‘The gradual movement of a substance from a region of high concentration to a region of low concentration.’ Which process is being described?

Oct/Nov 2020

Which gas diffuses at the slowest rate?

Oct/Nov 2020

Which gas diffuses at the lowest rate?

Oct/Nov 2020

Which gas diffuses at the slowest rate?

Oct/Nov 2020

Aqueous ammonium sulfate, $(\text{NH}_4)_2\text{SO}_4$, is heated with aqueous sodium hydroxide. Ammonia, $\text{NH}_3$, a pungent-smelling gas, is produced.

Oct/Nov 2020

The apparatus is arranged as shown. After a few minutes, a white ring of ammonium chloride forms in the position shown. Which statement accounts for the observation after several minutes?

Oct/Nov 2021

Brownian motion and gas diffusion give evidence for the particulate nature of matter. Which row shows an example of Brownian motion and how molecular mass controls the rate at which gas molecules diffuse?

Oct/Nov 2021

The diffusion rates of three gases, ammonia, carbon dioxide and methane, are measured. In order from the slowest diffusion rate to the fastest diffusion rate, what is the sequence of the gases?

Oct/Nov 2022

Which statement correctly describes Brownian motion?

Oct/Nov 2022

Which gas diffuses at the slowest rate?

Oct/Nov 2022

Four experiments, each one holding a different acidic gas, are arranged as shown. The glass partition plates are taken away simultaneously. In which apparatus arrangement does the litmus change to red first?

Oct/Nov 2023

Which of the following statements about the diffusion rates of ammonia, carbon monoxide, nitrogen and oxygen is correct?

Oct/Nov 2023

In what states of matter does diffusion happen readily?

Oct/Nov 2024

Which gas diffuses at the slowest rate at room temperature and pressure?

Oct/Nov 2024

Which process refers to a substance moving very slowly from a region of high concentration to a region of low concentration?

Oct/Nov 2025

A crystal of sodium chloride is placed into a beaker containing water. As time passes, the sodium chloride particles spread out uniformly through the water. Which processes take place in this experiment?

Oct/Nov 2025

Ammonia gas reacts with hydrogen chloride gas in the apparatus shown. Solid ammonium chloride is formed. Which statement explains why the solid ammonium chloride forms closer to the hydrogen chloride?

Oct/Nov 2025

A student studies the diffusion of ammonia gas, $\text{NH}_3$, and hydrogen chloride gas, $\text{HCl}$. Two apparatus setups are arranged as shown at room temperature and pressure. The damp red litmus paper in apparatus 1 changes colour after 30 seconds. How long will it take for the damp blue litmus paper in apparatus 2 to change colour?

Oct/Nov 2025

Which gas diffuses the fastest at room temperature and pressure?

Oct/Nov 2025