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Study of the 1st element Hydrogen

Exercise 6(A)

$l1. Justify the position of Hydrogen in the periodic table.

Ans. Position of hydrogen in the periodic table Hydrogen has atomic number 1 It has one electron in its atom Is electronic configuration is 1 (K-shell) It has one electron in its valence shell.

Hydrogen resembles with group I as well as group 17 elements. Also in certain properties hydrogen difFers from group and group 17 elements. But on account of its electronic configuration, it is generally placed with group I elements at their top

2. Why does hydrogen show dual nature ?

Ans, Hydrogen show dual nature i.s. it resembles with group I as well as group 17 elements. This is because hydrogen atom can lose or gain one electron

3. Compare hydrogen with alkali metals on the basis of :

(1) Ion formation (iii) Reaction with oxygen (it) Reducing power (iv) Oxide formation Ans. Comparison of hydrogen with alkali metals :

(i) On the basis of ion formation: Both hydrogen and alkali me of the one valence electron.
On the basis of reducing power: Both alkali metals and hydrogen are reducing agents.

(ü) On the basis of reaction with oxygen: Both alkali metals and hydrogen react with oxygen to give oxide.

(iv) On the basis of oxide formation: Both hydrogen and alkali metals burn in oxygen to form oxides. Hydrogen burn in air (or 0,) to form normal oxide i.e., H,O.

Lithium burn in oxygen to form lithium oxide.
Sodium burn in O, to form sodium peroxide (main product),Other alkali metals burn in oxygen to form superoxide with general formula MO, . For example,
K+O2-->KO2

 2. In what respect does hydrogen differs from (1) alkali metals (ii) halogens.

Ans. Points of difference of hydrogen from () Alkali metals Hydrogen has one shell whereas alkali elements have more than one shell.

The oxide of hydrogen, H,O is neutral whereas oxides of alkali metals (Na-0, K etc.) are basic in nature.

(ii) Halogens

1. Hydrogen has one shell whereas halogens have more than one shell.

2. The oxide of hydrogen, H,O is neutral whereas oxides of halogens like CLO.CI etc are acidic.

5. Give the general group study of hydrogen with the reference to (i) valence electron
(ii) Burning 
iii) reducing power.
Ans. 
Valency of electron : Hydrogen has one electron in its valence shell.

(ii) Burning : Hydrogen burns with pop sound in air or oxygen with a pale blue flame producin water

2H2 + O2 ->(burn)2H20 
(ii) Reducing power : Hydrogen gas is a strong reducing agent.

e.g. it reduces metal oxides to metals,

PbO + H2 -(heat)->Pb +H2O

Cu + H2-(heat)->Cu +H2O

16. Why was hydrogen called 'inflammable air' ?

Ans. Hydrogen was called inflammable air because it is combustible.

7. Staten some sources of hydrogen.

Ans. Sources of hydrogen:

These are:

1. Water                          3. Alkalis

2. Acids

8. Compare hydrogen and halogens on the basis of:

(i) physical state (ü) ion formation (iii) valency (iv) reaction with oxygen
Ans. Comparison of hydrogen with halogens :

(i) On the basis of physical state: At room temperature Is a gas. Among all the halogens, F, and Cl, are gases, Br, is a liquid while I is a solid at room temperature.

(ii) On the basis of ion formation: Just like halogens, hydrogen can accept one electron form a uninegative ion
(iii) On the basis of valency: Hydrogen can show a valency of -1 just like halogens by the gain of one electron.
(iv) On the basis of reaction with oxygen: Hydrogen burn in oxygen to form water whereas halogens do not react with oxygen in a similar manner. Halogens do combine with oxygen but indirectly. Compounds of fluorine and oxygen are called fluorides of oxygen while compounds of other halogens with oxygen are called oxides of corresponding halogens.

19. Which metal is preferred for the preparation of (a) from water (b) from acid. Ans. Preparation of hydrogen from:

(a) Water

- Iron

(b) Acid

Zinc
10.  Write the reaction of steam with red hot iron.

Why this reaction is considered as reversible reaction?

How the reaction can proceed continuously?

(i) Reaction of steam with red hot iron.

(ii) This reaction is considered reversible because Fe, can react with H, to form Fe and H2O

(iii) The reaction can be made to go only in one direction by continuously removing the Hus soon as it is formed, thus not allowing it to react with Fe,O, to give back the reactants.

11. Explain the unique nature of zinc and aluminium. Give balanced equations to support your explanation.

Ans. Zinc and aluminium react with acids as well as hot concentrated alkali to form hydrogen

and soluble salts.

Zinc :
Zn+H2so4-->ZnSO4+H2
Zn+2NaOH-->Na2ZnO2+H2

Aluminium:
2Al+3H2So4-->Al2(SO4)3 +3H2

2AL +2KOH+2H2O-->2NaALO2 + 3H2
                                            Rest of the solution with 6 b will be out by 22 May.

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