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Water Flashcards

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1
Q

What are the natural sources of water?

A

The natural sources of water include springs, rain, rivers, and seas.

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2
Q

What gases are found in water, and in what percentages?

A

In water, Nitrogen is 63.9%, Oxygen is 33.2%, and Carbon(iv)oxide is 2.9%.

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2
Q

How does the composition of gases in water compare to that in air?

A

In air, Nitrogen is 78%, Oxygen is 21%, and Carbon(iv)oxide is 0.02%, whereas in water, the percentages are 63.9% Nitrogen, 33.2% Oxygen, and 2.9% Carbon(iv)oxide.

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3
Q

What is the bond angle in a water molecule?

A

The bond angle in a water molecule is 104.5°.

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4
Q

What is the boiling and freezing point of pure water at atmospheric pressure?

A

The boiling point of pure water is 100°C, and the freezing point is 0°C.

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5
Q

At what temperature does water have its maximum density and minimum volume?

A

Water has its maximum density and minimum volume at 4°C.

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6
Q

What are the steps involved in the treatment of water for town supply?

A

The steps are Aeration and Sedimentation, Coagulation, Filtration, Disinfection, pH measurement, and Distribution.

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6
Q

What causes the hardness of water?

A

The hardness of water is caused by the presence of soluble bicarbonates, chlorides, and sulfates of calcium and magnesium.

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6
Q

How can temporary hardness of water be removed?

A

Temporary hardness can be removed by boiling or adding slaked lime (calcium hydroxide) or washing soda (Na2CO3).

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7
Q

What is the purpose of adding chlorine, iodine, and fluorine during water treatment?

A

Chlorine is added to kill bacteria, iodine is added to prevent goitre, and fluorine is added to prevent tooth decay.

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8
Q

What are the categories of metals based on their reactivity with water?

A

Metals are categorized as active, semi-active, and non-reactive based on their reactivity with water.

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8
Q

How do active metals react with water?

A

Active metals react strongly with water to produce hydrogen gas and an alkaline solution in an exothermic reaction.

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8
Q

How can permanent hardness of water be removed?

A

Permanent hardness can be removed by distillation, addition of washing soda, or using permutit (NaAlSiO4), which acts as a cation exchange resin.

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9
Q

What happens when water reacts with white anhydrous CuSO4?

A

When water reacts with white anhydrous CuSO4, it turns blue.

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10
Q

Why is water referred to as a universal solvent?

A

Water is referred to as a universal solvent because it dissolves many substances such as acids, salts, sugars, and gases.

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10
Q

What is the color change when water reacts with blue anhydrous Cobalt(ii) chloride?

A

The color changes from blue to pink.

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10
Q

What are the disadvantages of hard water?

A

Hard water wastes soap, forms fur in kettles, and is not suitable for drug production and tanning.

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10
Q

What is the anomalous expansion of water?

A

Unlike other liquids, water contracts when heated from 0°C until it reaches 4°C, after which it expands. This is called the anomalous expansion of water.

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10
Q

What is the water cycle?

A

The water cycle is a biogeochemical cycle involving the continuous movement of water on, above, and below the Earth’s surface.

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11
Q

What are the advantages of hard water?

A

Hard water provides calcium salts for manufacturing processes, supports shell formation in aquatic animals, aids in bone and teeth development, and is preferred in brewing beer.

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11
Q

What are the disadvantages of soft water?

A

Soft water attacks lead pipes, has an insipid taste, and lacks calcium salts necessary for bone and teeth development.

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12
Q

Q22: How can you test if water is pure?

A

You can test water purity by checking if it boils at 100°C, freezes at 0°C, and has a density of 1.0g/cm³ at 4°C.

13
Q

What is the chemical equation for the combustion of hydrogen to form water?

A

2H₂ + O₂ → 2H₂O

13
Q

What is the composition of water produced from the combustion of hydrogen?

A

Water is composed of two hydrogen atoms and one oxygen atom (H₂O). In volume terms, water vapor is made up of 2 volumes of hydrogen and 1 volume of oxygen.

14
Q

Why is water considered a universal solvent?

A

Water is considered a universal solvent because its polar nature allows it to dissolve many substances.

15
Q

What atmospheric gases are commonly dissolved in water?

A

Oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂) are commonly dissolved in water.

16
Q

What is the role of dissolved carbon dioxide in water?

A

Dissolved carbon dioxide forms carbonic acid, which helps regulate the pH of water and is used by aquatic plants during photosynthesis.

17
Q

What is the biological significance of dissolved oxygen in water?

A

Dissolved oxygen is essential for the respiration of aquatic organisms and supports life in aquatic environments.

18
Q

What is hard water?

A

Hard water contains high concentrations of calcium and magnesium ions, which can lead to scale formation in pipes and appliances.

19
Q

What is soft water?

A

Soft water contains low concentrations of calcium and magnesium ions and does not form scale easily.

20
Q

What are the main steps in the treatment of water for town supply?

A

The main steps include coagulation and flocculation, sedimentation, filtration, and disinfection.

20
Q

What causes temporary hardness in water?

A

Temporary hardness is caused by the presence of dissolved bicarbonates (HCO₃⁻), which can be removed by boiling.

21
Q

What causes permanent hardness in water?

A

Permanent hardness is caused by the presence of dissolved sulfates (SO₄²⁻) or chlorides (Cl⁻) of calcium and magnesium, which cannot be removed by boiling.

22
Q

Why is filtration important in water treatment?

A

Filtration removes smaller particles and contaminants that remain after coagulation and sedimentation.

22
Q

Give an example of a substance with water of crystallization.

A

Copper(II) sulfate pentahydrate (CuSO₄·5H₂O) is an example of a substance with water of crystallization.

23
Q

What is one method to remove permanent hardness from water?

A

Using ion exchange resins or adding chemical softeners like washing soda (sodium carbonate) can remove permanent hardness.

24
Q

What is one method to remove temporary hardness from water?

A

Boiling the water precipitates calcium carbonate (CaCO₃), which can be removed.

24
Q

What is the purpose of disinfection in water treatment?

A

Disinfection kills or inactivates harmful microorganisms to ensure the water is safe to drink.

25
Q

What is deliquescence?

A

Deliquescence is the process where a substance absorbs moisture from the air and dissolves in the absorbed water to form a solution.

25
Q

What is water of crystallization?

A

Water of crystallization is water that is incorporated into the crystalline structure of a substance.

25
Q

What is the purpose of coagulation and flocculation in water treatment?

A

Coagulation and flocculation aggregate suspended particles into larger clumps (flocs) that can be removed from the water.

26
Q

What is efflorescence?

A

Efflorescence is the process where a crystalline substance loses its water of crystallization to the air and becomes powdery.

27
Q

Give an example of a substance that exhibits efflorescence.

A

Sodium carbonate decahydrate (washing soda, Na₂CO₃·10H₂O) is an example of a substance that exhibits efflorescence.

28
Q

Give an example of a deliquescent substance.

A

Calcium chloride (CaCl₂) is an example of a deliquescent substance.

29
Q

What is hygroscopy?

A

Hygroscopy is the ability of a substance to attract and hold moisture from the air without dissolving.

30
Q

Give an example of a hygroscopic substance.

A

Silica gel is an example of a hygroscopic substance.

31
Q

What are the various uses of water?

A

Water is used for drinking, irrigation, industrial processes, transportation, and sanitation.

32
Q

What are the effects of dissolved atmospheric gases in water?

A

Dissolved gases affect the water’s pH, support aquatic life, and influence water’s chemical properties.

33
Q

How do you distinguish between hard and soft water?

A

Hard water forms scale and reacts with soap to form scum, while soft water does not form scale and produces a lather with soap.

34
Q

What are the causes of hardness in water?

A

Hardness is caused by the presence of dissolved calcium and magnesium ions.

35
Q

What methods can be used to remove hardness from water?

A

Hardness can be removed by boiling, using ion exchange resins, or adding chemical softeners like washing soda.

36
Q

What are the processes involved in the treatment of water for town supply?

A

The processes include coagulation and flocculation, sedimentation, filtration, and disinfection.

37
Q

How do you distinguish between efflorescence, deliquescence, and hygroscopy?

A

Efflorescence involves losing water to the air, deliquescence involves absorbing moisture to form a solution, and hygroscopy involves attracting moisture without dissolving.

38
Q

What are some compounds that exhibit water of crystallization, efflorescence, deliquescence, and hygroscopy?

A

Water of crystallization: Copper(II) sulfate pentahydrate; Efflorescence: Sodium carbonate decahydrate; Deliquescence: Calcium chloride; Hygroscopy: Silica gel.

Chemistry (17 decks)

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