What colour does cobalt chloride paper turn in the presence of water?

Cobalt chloride paper turns from blue to pink in the presence of water. This colour change shows that water is present.

Anhydrous copper(II) sulfate turns from ______ to ______ when water is added.

Anhydrous copper(II) sulfate turns from white to blue when water is added.

What is the symbol equation for anhydrous copper(II) sulfate reacting with water?

The symbol equation for anhydrous copper(II) sulfate reacting with water is: CuSO 4 (s) + 5H 2 O (l) ⇌ CuSO 4 .5H 2 O (s) The anhydrous form is white and the hydrated form is blue.

Complete the equation for the hydration of cobalt(II) chloride: CoCl 2 (s) + ______ H 2 O (l) ⇌ CoCl 2 . ______ H 2 O (s)

The equation for the hydration of cobalt(II) chloride is: CoCl 2 (s) + 6 H 2 O (l) ⇌ CoCl 2 . 6 H 2 O (s)

True or False? Impurities in water raise its boiling point above 100 °C.

True. Impurities dissolve in water and interact with the molecules, requiring more energy to boil the liquid, so impure water boils at a temperature above 100 °C.

Impurities tend to ______ the melting point of water, so impure water melts below 0 °C.

Impurities tend to decrease the melting point of water, so impure water melts below 0 °C.

Why is distilled water used in practical chemistry rather than tap water?

Distilled water is used because it contains very few impurities. Tap water contains dissolved substances that could interfere with chemical reactions and affect the results.

Water from natural sources may contain dissolved ______ , metal compounds, plastics, sewage, harmful microbes, and ______ and phosphates from fertilisers.

Water from natural sources may contain dissolved oxygen , metal compounds, plastics, sewage, harmful microbes, and nitrates and phosphates from fertilisers.

Water from natural sources may contain ______ from fertilisers, which can lead to deoxygenation of water.

Water from natural sources may contain nitrates from fertilisers, which can lead to deoxygenation of water. Phosphates from fertilisers have the same effect.

Which dissolved substances in natural water are beneficial to living organisms?

Dissolved oxygen is essential for aquatic life. Some metal compounds, such as calcium and magnesium compounds, provide essential minerals that are necessary for life.

Metal compounds in water can be harmful if they contain toxic metals such as ______ or lead.

Metal compounds in water can be harmful if they contain toxic metals such as aluminium or lead.

True or False? Sewage in natural water sources is harmful because it contains microbes that can cause disease.

True. Sewage contains harmful microbes that, if consumed, can cause disease in humans, making contaminated water unsafe to drink.

Plastics in natural water can harm aquatic life by filling animals' stomachs so they die of ______ .

Plastics in natural water can harm aquatic life by filling animals' stomachs so they die of starvation .

Why are nitrates and phosphates from fertilisers considered harmful when they enter water sources?

Nitrates and phosphates from fertilisers promote the excessive growth of aquatic plants. This leads to deoxygenation of the water, which damages aquatic life.

What is sedimentation in water treatment?

Sedimentation is the process in which water is left to stand so that mud, sand and other particles settle to the bottom of the tank due to gravity.

During filtration in water treatment, water is passed through layers of ______ and ______ that trap solid particles.

During filtration in water treatment, water is passed through layers of sand and gravel that trap solid particles.

Why is chlorination used in water treatment rather than filtration alone?

Bacteria and other microorganisms are too small to be trapped by filtration. Chlorination involves adding chlorine to the water to kill these bacteria, making the water safe to drink.

Water is taken from rivers, ______ or underground sources known as groundwater.

Water is taken from rivers, reservoirs or underground sources known as groundwater.

True or False? Passing water through carbon (charcoal) removes bacteria from the water supply.

False. Carbon removes tastes and odours from water, but it does not kill bacteria. Bacteria are killed by chlorination.

______ and typhoid are examples of bacterial diseases that can arise from drinking untreated water.

Cholera and typhoid are examples of bacterial diseases that can arise from drinking untreated water.

What types of impurity are found in untreated water, and how are they removed?

Untreated water contains insoluble impurities (removed by sedimentation and filtration) and soluble impurities such as dissolved metal compounds. Bacteria are removed by chlorination.

O LevelChemistryCambridge (CIE)Flashcards10. Chemistry of the Environment10.1 Water & Water Pollution

10.1 Water & Water Pollution (Cambridge (CIE) O Level Chemistry): Flashcards

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What colour does cobalt chloride paper turn in the presence of water?

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Cards in this collection (21)

What colour does cobalt chloride paper turn in the presence of water?
Cobalt chloride paper turns from blue to pink in the presence of water. This colour change shows that water is present.
Anhydrous copper(II) sulfate turns from ______ to ______ when water is added.
Anhydrous copper(II) sulfate turns from white to blue when water is added.
What is the symbol equation for anhydrous copper(II) sulfate reacting with water?
The symbol equation for anhydrous copper(II) sulfate reacting with water is:
CuSO₄ (s) + 5H₂O (l) ⇌ CuSO₄.5H₂O (s)
The anhydrous form is white and the hydrated form is blue.
Complete the equation for the hydration of cobalt(II) chloride:
CoCl₂ (s) + ______ H₂O (l) ⇌ CoCl₂.______H₂O (s)
The equation for the hydration of cobalt(II) chloride is:
CoCl₂ (s) + 6H₂O (l) ⇌ CoCl₂.6H₂O (s)
True or False?
Impurities in water raise its boiling point above 100 °C.
True.
Impurities dissolve in water and interact with the molecules, requiring more energy to boil the liquid, so impure water boils at a temperature above 100 °C.
Impurities tend to ______ the melting point of water, so impure water melts below 0 °C.
Impurities tend to decrease the melting point of water, so impure water melts below 0 °C.
Why is distilled water used in practical chemistry rather than tap water?
Distilled water is used because it contains very few impurities. Tap water contains dissolved substances that could interfere with chemical reactions and affect the results.
Water from natural sources may contain dissolved ______, metal compounds, plastics, sewage, harmful microbes, and ______ and phosphates from fertilisers.
Water from natural sources may contain dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, and nitrates and phosphates from fertilisers.
Water from natural sources may contain ______ from fertilisers, which can lead to deoxygenation of water.
Water from natural sources may contain nitrates from fertilisers, which can lead to deoxygenation of water.
Phosphates from fertilisers have the same effect.
Which dissolved substances in natural water are beneficial to living organisms?
Dissolved oxygen is essential for aquatic life. Some metal compounds, such as calcium and magnesium compounds, provide essential minerals that are necessary for life.
Metal compounds in water can be harmful if they contain toxic metals such as ______ or lead.
Metal compounds in water can be harmful if they contain toxic metals such as aluminium or lead.
True or False?
Sewage in natural water sources is harmful because it contains microbes that can cause disease.
True.
Sewage contains harmful microbes that, if consumed, can cause disease in humans, making contaminated water unsafe to drink.
Plastics in natural water can harm aquatic life by filling animals' stomachs so they die of ______.
Plastics in natural water can harm aquatic life by filling animals' stomachs so they die of starvation.
Why are nitrates and phosphates from fertilisers considered harmful when they enter water sources?
Nitrates and phosphates from fertilisers promote the excessive growth of aquatic plants. This leads to deoxygenation of the water, which damages aquatic life.
What is sedimentation in water treatment?
Sedimentation is the process in which water is left to stand so that mud, sand and other particles settle to the bottom of the tank due to gravity.
During filtration in water treatment, water is passed through layers of ______ and ______ that trap solid particles.
During filtration in water treatment, water is passed through layers of sand and gravel that trap solid particles.
Why is chlorination used in water treatment rather than filtration alone?
Bacteria and other microorganisms are too small to be trapped by filtration. Chlorination involves adding chlorine to the water to kill these bacteria, making the water safe to drink.
Water is taken from rivers, ______ or underground sources known as groundwater.
Water is taken from rivers, reservoirs or underground sources known as groundwater.
True or False?
Passing water through carbon (charcoal) removes bacteria from the water supply.
False.
Carbon removes tastes and odours from water, but it does not kill bacteria. Bacteria are killed by chlorination.
______ and typhoid are examples of bacterial diseases that can arise from drinking untreated water.
Cholera and typhoid are examples of bacterial diseases that can arise from drinking untreated water.
What types of impurity are found in untreated water, and how are they removed?
Untreated water contains insoluble impurities (removed by sedimentation and filtration) and soluble impurities such as dissolved metal compounds. Bacteria are removed by chlorination.

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