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9.36  What do you understand by the terms: (i) hydrogen economy (ii) hydrogenation (iii) ‘syngas’ (iv) water-gas shift reaction (v) fuel-cell ?

(i)Hydrogen Economy- Technique of using dihydrogen in an efficient way. The basic principle of the hydrogen economy is the transportation and storage of energy in the form of liquid or gaseous dihydrogen.  (ii)Hydrogenation- The addition of dihydrogen to the reactant. This process can be done with the help of a suitable catalyst like nickel and palladium. (iii)Syngas-  The mixture of  . This...

9.35  How does H2O2 behave as a bleaching agent?

Hydrogen peroxide   act as an oxidizing agent in basic as well as the acidic medium. In the exposure of light, it decomposes and gives nascent oxygen which combines with coloring matter which in turn gets oxidized. So the bleaching action of  is mainly due to the oxidation of coloring matter.

9.34  Do you expect different products in solution when aluminum (III) chloride and potassium chloride treated separately with (i) normal water (ii) acidified water, and (iii) alkaline water? Write equations wherever necessary.

Answer- KCl is salt of KOH(strong base) and HCl(strong acid). So it does not hydrolyze in normal water because it is neutral in nature. It just simply ionizes in water.           In acidified and alkaline water they do not dissociate into ions and remains the same.  is the salt of a weak base   and HCl( strong acid).So it hydrolyzes in normal water.                   In acidic water, there...

9.33 What do you expect the nature of hydrides is, if formed by elements of atomic numbers 15, 19, 23 and 44 with dihydrogen? Compare their behaviour towards water

Answer- Atomic Number 15 19 23 and 44 are phosphorus, potassium, vanadium, and ruthenium respectively. hydrides of these elements are  (i)- its an electron rich species also a covalent molecule.            a lone pair of electron. (ii)Hydrides of potassium- dihydrogen forms an ionic hydride. It is crystalline and non-volatile in nature       (iii) hydrides of vanadium and ruthenium- Both...

9.32  How can saline hydrides remove traces of water from organic compounds?

The saline hydrides react with water to form metal hydroxide and liberate hydrogen gas. reaction-      [M = Na, K, Ca...] when added to the organic compounds they form metal hydroxide along with the liberation of hydrogen gas (escape into the atmosphere) and leave behind only hydroxide part.

9.31  What is the difference between the terms ‘hydrolysis’ and ‘hydration’ ?

Hydrolysis- it means the reaction of the water molecule with another compound and forming a new product. for example.                  Hydration- It means the addition of one or more than one water molecule to form a hydrated compound.   ex.

9.30  Knowing the properties of H2O and D2O, do you think that D2O can be used for drinking purposes?

is heavy water, it acts as a moderator which slow down the rate of the chemical reaction. Due to this property, we cannot use it for drinking purpose. if we use, it will slow down our metabolic reaction happens in the body.

9.29 What properties of water make it useful as a solvent? What types of a compound can it (i) dissolve, and (ii) hydrolyze?

Water has high dielectric constant () and dipole moment which makes it universal solvent. It dissolves the most ionic as well as covalent compounds. [ionic compound because of ion-dipole interaction and covalent due to their tendency to form a hydrogen bond with water.] Water is also able to hydrolyze the metallic and non-metallic oxides, hydrides and nitrides, etc.

9.28  Describe the usefulness of water in biosphere and biological systems.

Water is essential for all living beings. It plays an important role in the biosphere. its has high specific heat, thermal conductivity, surface tension, dipole moment, and dielectric constant. The high heat of vaporisation and heat capacity are responsible for the moderation of the climate and body temperature of living beings. It is  an excellent solvent for transportation of ions and...

9.27 Is demineralized or distilled water useful for drinking purposes? If not, how can it be made useful?

Water contains several minerals that are necessary or required by human beings, plants, animals for survival. And we know that demineralized water is free from all these minerals. So it is not useful for drinking purpose. It can be made useful by adding desired minerals in a certain amount which are favourable for growth.

9.26  What is meant by ‘demineralised’ water and how can it be obtained?

Demineralized water means free from all types of cations and anions and also soluble mineral salts. It can be obtained by passing water successively through a cation exchange (in the  ion form) and anion exchange (in the form of ion) resins: Cation exchange process-     {  exchange for  and other cation present in water.} Anion exchange process-   exchanges for anions like  etc present in the...

9.24  Write chemical reactions to show the amphoteric nature of water.

It has the ability to act as an acid as well as a base. In the Bronsted sense, it acts as an acid with ammonia and a base with hydrogen sulphide. Reactions to show the amphoteric nature of water -

9.23  Discuss the principle and method of softening of hard water by synthetic ionexchange resins.

The treatment process of permanent hard water using synthetic resin is based on cations exchange  and anion exchange  ;present in water by ions and ions. There are two types- (i) Cation exchange resins (ii)anion exchange resins Cation exchange resin is large organic molecules contain   group and are water-insoluble.  Ion exchange resin (RSO3H) is changed to RNa by treating it with NaCl. The...

9.22  What causes the temporary and permanent hardness of water ?

Answer- Temporary hardness of water is because of the presence of salts of magnesium and calcium hydrogen carbonates. [ M = Mg,Ca]. Permanent hardness is due to the presence of soluble salts of magnesium and calcium in the form of chlorids and sulphates in water. e.g,  [M = Mg and Ca]

9.21  Describe the structure of the common form of ice.

Answer-  Ice is a crystalline form of water. At atmospheric pressure, ice crystallizes in the hexagonal form, but at low temperature, it condenses to cubic form. The density of ice is less than water; therefore it floats on the water surface. Ice has a highly ordered three-dimensional hydrogen-bonded structure. (shown above) Each Oxygen atom is surrounded by four H atom tetrahedrally.

9.20 Complete the following chemical reactions

(v)   $Ca_{3}N_{2}(s)+H_{2}O(l)\rightarrow$

Classify the above into (a) hydrolysis, (b) redox and (c) hydration reactions

Answer- the complete reaction is -  The reaction in which water reacts with water and produce other compound are called hydrolysisreaction.

9.20 (iv) Complete the following chemical reactions

$AlCl_{3}(g)+H_{2}O(l)\rightarrow$

Classify the above into (a) hydrolysis, (b) redox and (c) hydration reactions.

Answer- The complete reaction is - The given reaction is hydrolysis reaction.

9.20  Complete the following chemical reactions.

(iii) $CaO(s)+H_{2}O(g)\rightarrow$

Classify the above into (a) hydrolysis, (b) redox and (c) hydration reactions

Answer- The reaction is -   it is a hydrolysis reaction because we know that the reaction in which water reacts with water to produce another compound is  hydrolysis.

9.20 Complete the following chemical reactions.

(ii) $MnO_{4}^{-}(aq)+H_{2}O_{2}(aq)\rightarrow$

Classify the above into (a) hydrolysis, (b) redox and (c) hydration reactions.

Answer- Reaction is-  Here hydrogen peroxide reduces the  into act as reducing agent. Hence it's a redox reaction.

9.20 Complete the following chemical reactions.

$(i)PbS(s)+H_{2}O_{2}(aq)\rightarrow$

Classify the above into (a) hydrolysis, (b) redox and (c) hydration reactions

Here hydrogen peroxide oxidizes the lead sulfide, act as an oxidising agent. Hence it is a redox reaction.
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