Water

Which pollutant is responsible for eutrophication in rivers?

May/June 2016

Dissolved minerals and gases are present in river water.

May/June 2016

Substances dissolved in water may lead to eutrophication. How many of the ions shown bring about this effect? $Cl^-$, $CO_3^{2-}$, $Na^+$, $NO_3^-$, $PO_4^{3-}$

May/June 2017

Seawater is desalinated so that it becomes safe to drink. Which main substance does desalination remove?

May/June 2018

Which treatment process is used for water disinfection?

May/June 2019

Drinking water is produced by purifying sea water and river water.

May/June 2019

What is one cause of deoxygenation of lake water?

May/June 2023

Dissolved substances may lead to eutrophication and deoxygenation of water. How many of the ions shown here cause this effect? $\text{Cl}^-$, $\text{CO}_3^{2-}$, $\text{Na}^+$, $\text{NO}_3^-$, $\text{PO}_4^{3-}$

May/June 2023

What makes carbon suitable for water purification?

May/June 2023

Which compound has the lowest solubility in water?

May/June 2024

Chlorine and carbon are both used to treat the domestic water supply. Which row describes one reason for using each substance?

May/June 2025

Domestic water is treated before it reaches homes. Three treatments are given: sedimentation and filtration; treatment with chlorine; treatment with carbon. Which row indicates the purpose of these treatments?

May/June 2025

The flow chart illustrates how impure water can be treated to produce water that is safe to drink. What is not removed from the water by this process?

Oct/Nov 2015

The flow chart illustrates how contaminated water may be processed to produce water that is safe to drink. Which substance is not removed from the water by this process?

Oct/Nov 2015

Carbon and chlorine are used to treat water supplied for domestic use.

Oct/Nov 2015

The table outlines treatments applied to drinking water supplies and the reasons for applying them. Which row is correct?

Oct/Nov 2016

What gets removed or destroyed when water is desalinated so that it becomes safe to drink?

Oct/Nov 2017

What is the purpose of adding chlorine to the water supply?

Oct/Nov 2017

A number of different treatments are used to clean the water supply. Which impurities are removed by each treatment?

Oct/Nov 2018

The water supply is purified by filtration and chlorination. After these treatments, which substance is still present in the water supply?

Oct/Nov 2019

Two statements concerning the water in lakes are provided.

Oct/Nov 2020

During water purification, four processes are employed: • use of carbon • desalination • chlorination • filtration The aims, W, X, Y and Z, of these processes are given below. W: disinfection X: removal of solids Y: removal of dissolved salts Z: removal of tastes and odours What is the purpose of each process?

Oct/Nov 2020

Carbon is used to purify the water supply. Why is it used?

Oct/Nov 2022

Which statement concerning natural water sources and the domestic water supply is correct?

Oct/Nov 2023

Which statement regarding water is correct?

Oct/Nov 2023

The water supplied to homes is treated so that it is safe to drink. Which row identifies the treatment and its effect?

Oct/Nov 2024

Three liquids, X, Y and Z, are examined, and the outcomes are given below. Tests: • add anhydrous cobalt(II) chloride: X changes from blue to pink, Y no change, Z changes from blue to pink • measure boiling point: X $100^\circ\text{C}$, Y $78^\circ\text{C}$, Z $103^\circ\text{C}$ What can be inferred about X, Y and Z from this evidence?

Oct/Nov 2024

Which substance is added to eliminate odours when treating domestic water supplies?

Oct/Nov 2025

Water can include several substances before it is made safe to drink. Three substances are shown. Which of these are taken out during treatment of the domestic water supply?

Oct/Nov 2025

Water forms an essential component of the environment.

Oct/Nov 2025