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Aperçu

Welcome to the detailed overview of the Chemistry course material focusing on the topic of Water. In this section, we will delve into various aspects related to water, including its composition, properties, uses, and treatment methods.

Water is an essential molecule for life on Earth, with a wide range of uses in various fields. It is composed of two hydrogen atoms bonded to one oxygen atom, forming a polar molecule with unique properties. One crucial aspect to understand is that water can dissolve a variety of substances due to its polarity, making it a universal solvent.

One of the key objectives of this course is to identify the effects of dissolved atmospheric gases in water. Water can dissolve gases such as oxygen, carbon dioxide, and nitrogen from the atmosphere. These dissolved gases play vital roles in biological processes, such as respiration and photosynthesis, highlighting the importance of understanding water as a solvent.

Furthermore, we will distinguish between the properties of hard and soft water. Hard water contains high levels of dissolved minerals, primarily calcium and magnesium ions, which can lead to issues such as scale buildup in pipes and appliances. On the other hand, soft water has lower mineral content and is preferred for tasks like laundry and bathing.

To address the challenges posed by hard water, it is crucial to identify the causes of hardness and explore methods for its removal. Techniques such as ion exchange, distillation, and reverse osmosis are commonly employed to soften hard water and improve its usability in various applications.

Another critical aspect we will cover is the treatment of water for town supply. Ensuring access to clean and safe drinking water involves processes like filtration, chlorination, and fluoridation to remove contaminants and microorganisms. Understanding these treatment methods is vital for maintaining public health and preventing waterborne diseases.

Lastly, we will explore phenomena related to water crystallization, efflorescence, deliquescence, and hygroscopy. These phenomena involve the absorption and release of water molecules by certain compounds, leading to distinct physical changes. By studying examples of substances exhibiting these properties, such as hydrated salts and desiccants, we can appreciate their practical applications in various industries.

Objectifs

Determine The Causes Of Hardness
Identify The Various Uses Of Water
Distinguish Between These Phenomena
Distinguish Between The Properties Of Hard And Soft Water
Describe The Processes Involved In The Treatment Of Water For Town Supply
Identify The Various Compounds That Exhibit These Phenomena
Identify The Effects Of Dissolved Atmospheric Gases In Water
Identify Methods Of Removal Of Hardness

Note de cours

Composition of Water

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Évaluation de la leçon

Félicitations, vous avez terminé la leçon sur Water. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.

Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.

Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.

What is the main difference between hard water and soft water? A. Amount of minerals dissolved in water B. Presence of impurities in water C. Temperature at which water freezes D. pH level of the water Answer: A. Amount of minerals dissolved in water
Which of the following is NOT a method of softening hard water? A. Distillation B. Ion exchange C. Filtration D. Boiling Answer: C. Filtration
What is the purpose of adding chlorine during the treatment of water for town supply? A. To remove hardness B. To kill bacteria and viruses C. To improve taste D. To reduce pH level Answer: B. To kill bacteria and viruses
Efflorescence is the loss of water of crystallization by a compound due to exposure to air. Which substance commonly exhibits efflorescence? A. Sodium chloride B. Magnesium sulfate C. Calcium carbonate D. Potassium permanganate Answer: A. Sodium chloride
Which phenomenon involves the gradual uptake of water vapor from the air by a compound? A. Hygroscopy B. Deliquescence C. Efflorescence D. Condensation Answer: A. Hygroscopy

Livres recommandés

	Chemistry: The Central Science Sous-titre Hard and Soft Water and Water of Crystallization Éditeur Prentice Hall Année 2017 ISBN 978-0134414232
	Chemistry: Principles and Reactions Sous-titre Treatment of Water and Atmospheric Gases Éditeur Cengage Learning Année 2019 ISBN 978-1337399373

Questions précédentes

Vous vous demandez à quoi ressemblent les questions passées sur ce sujet ? Voici plusieurs questions sur Water des années précédentes.

JAMB UTME - Chemistry - 2023 (Cliquez pour passer l'évaluation complète)

Question 1 Rapport

Which of the following methods is commonly used to remove suspended impurities from water?

Fluoridation

Chlorination

Filtration

Distillation

Détails de la réponse

The Filtration method is commonly used to remove suspended impurities from water.

When water is obtained from natural sources such as rivers, lakes, or groundwater, it often contains various suspended impurities. These impurities can include particles like sand, clay, silt, and organic matter. These impurities make the water cloudy or turbid and can also affect its taste and smell.

Filtration is the process of passing water through a porous material or medium to separate and remove the suspended impurities. The porous material used in filtration is typically sand, activated carbon, or a combination of different layers of materials.

As the water flows through the filtration medium, the suspended impurities get trapped and retained in the tiny pores or gaps within the material. This effectively removes the impurities from the water, resulting in clearer and cleaner water.

Filtration is a widely used method in water treatment plants, households, and industries to improve the quality of water. It is an essential step in the treatment of drinking water to ensure that it is safe for consumption.

Other methods mentioned, such as Fluoridation, Chlorination, and Distillation, serve different purposes in water treatment:

- Fluoridation: This process involves adding a controlled amount of fluoride to drinking water to help prevent tooth decay. It is not primarily used to remove suspended impurities from water. - Chlorination: This process involves adding chlorine to water to disinfect it and kill harmful microorganisms. While chlorination can help remove some suspended impurities, its main purpose is to disinfect water. - Distillation: This method involves heating water to create steam, which is then cooled and collected as purified water. Distillation is effective in removing impurities but is less commonly used on a large scale due to its energy-intensive nature.

In conclusion, Filtration is the most commonly used method to remove suspended impurities from water, ensuring that it is clear, clean, and suitable for various applications.

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NECO SSCE - Chemistry - 2009 (Cliquez pour passer l'évaluation complète)

Question 1 Rapport

Sulphur has an oxidation number of +4 in

H₂S

H₂S0₄

MgSO₄

Na₂SO₃

S0₃

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WAEC SSCE - Chemistry - 2021 (Cliquez pour passer l'évaluation complète)

Question 1 Rapport

(a)i. With the aid of an equation, explain briefly why aluminum metal is not affected by air.

(ii) In the extraction of aluminum from bauxite, state the:
- substance used for purifying the ore;
- composition of the mixture electrolyzed.

(b) ZnO is an amphoteric oxide. Write equations to illustrate this statement.

(c)i) List three uses of sodium trioxocarbonate(IV).

(ii) Explain briefly why a solution of trioxonitrate(V) acid turns yellowish on storage for some time.

(ii) Describe briefly how trioxonitrate(V) ions could be tested for in the laboratory.

(d) Write balanced chemical equations for the preparation of hydrogen chloride.

(i) using concentrated H\(_{2}\)SO\(_{4}\):

(ii) by direct combination of its constituent elements.

(iii) State one use of hydrogen chloride.

Réponse

(a) (i) Aluminum metal is not affected by air because it is covered with a thin layer of aluminum oxide (Al2O3) that protects the metal from further oxidation. The equation for the formation of aluminum oxide is: 2Al + 3O2 → 2Al2O3 The aluminum oxide layer is very stable and prevents oxygen in the air from reaching the aluminum metal, thus protecting it from further reaction. (ii) In the extraction of aluminum from bauxite: - The substance used for purifying the ore is concentrated sodium hydroxide (NaOH) solution, which is used to dissolve the aluminum oxide (Al2O3) present in bauxite, leaving behind impurities. - The composition of the mixture electrolyzed is a molten mixture of aluminum oxide (Al2O3) and cryolite (Na3AlF6), which is used as a solvent to lower the melting point of Al2O3 and make it easier to extract aluminum by electrolysis. (b) ZnO is an amphoteric oxide, which means it can react with both acids and bases. The equations to illustrate this statement are: ZnO + 2HCl → ZnCl2 + H2O ZnO + 2NaOH + H2O → Na2Zn(OH)4 In the first equation, ZnO reacts with hydrochloric acid (HCl) to form zinc chloride (ZnCl2) and water (H2O). In the second equation, ZnO reacts with sodium hydroxide (NaOH) and water (H2O) to form sodium zincate (Na2Zn(OH)4). (c) (i) Three uses of sodium trioxocarbonate(IV) (sodium carbonate, Na2CO3) are: - It is used in the production of glass, where it acts as a flux to lower the melting point of silica (SiO2) and help it fuse into glass. - It is used as a water softener in laundry detergents, where it reacts with hard water ions (such as calcium and magnesium) to form insoluble precipitates that can be removed from clothing. - It is used as a food additive, where it acts as a leavening agent in baked goods to produce carbon dioxide (CO2) gas and make the dough rise. (ii) A solution of trioxonitrate(V) acid (HNO3) turns yellowish on storage for some time because it slowly decomposes to form nitrogen dioxide (NO2) gas, which is a brownish color. The equation for this decomposition is: 4HNO3 → 2H2O + 4NO2 + O2 (iii) Trioxonitrate(V) ions (NO3-) can be tested for in the laboratory using the Brown Ring Test. In this test, a solution of the sample containing NO3- ions is mixed with freshly prepared iron(II) sulfate (FeSO4) solution and concentrated sulfuric acid (H2SO4). A brown ring will form at the junction of the two layers if NO3- ions are present, due to the formation of a complex between Fe2+ ions, NO3- ions, and H2O molecules. (d) (i) The balanced chemical equation for the preparation of hydrogen chloride (HCl) using concentrated sulfuric acid (H2SO4) is: NaCl + H2SO4 → NaHSO4 + HCl (ii) The balanced chemical equation for the preparation of hydrogen chloride (HCl) by direct combination of its constituent elements is: H2 + Cl2 → 2HCl (iii) One use

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