a) In most cases the first letter of an element was taken as the symbol for that element. Give two examples of the same.
b) In certain cases the first letter along with its small letter from its name were used as the symbols. Give two examples of the same.
c) In some cases the symbols for derived from their Latin names. Name two metals whose symbols are derived from the same.
d) Sulphur is represented by the symbol 'S'. State how the symbol represents the elements
i) qualitatively (i.e., representation in terms of an atom)
ii) quantitatively,(i.e., representation in terms of weight)
B) 1) Explain the meaning of terms in Italics given below.
For writing a chemical formula the symbols and the valency of the element or radical should be known:
2) Give reasons for the following :
i) In hydrogen chloride the valency of the element chlorine is considered as one.
ii) Certain metals exhibit more than one valency and showing 'variable valancy'.
C) State the valency and name the ion or radical in each of the following cases given below (the first example is completed for you)
Electrovalent positive ions or radicals
Symbol/Valency Name
1) K¹⁺ potassium
2) Na
3) H
4) NH₄
5) Ca
6) Mg
7) Zn
8) Ba
9) Ni
10) Co
11) Al
Variable valencies
1) Cu¹⁺
2) Cu
3) Hg¹⁺
4) Hf
5) Fe²⁺
6) Fe
7) Mn²⁺
8) Mn
9) Pb²⁺
10) Pb
11) Pt²⁺
12) Pt
Electrovalent negative ion or radicals
1) Cl¹⁻ chloride
2) ClO₃
3) ClO
4) Br
5) I
6) OH
7) NO₂
8) NO₃
9) HCO₃
10) HSO₃
11) HSO₄
12) AlO₂
13) MnO₄
14) SO₃
15) SO₄
16) S
17) CO₃
18) O
19) CrO₄
20) Cr₂O₇
21) ZnO₂
22) PbO₂
23) PO₄
24) N
25) C
B2) State the valency of each of the elements in the respective compounds given below
a) sulphur in i) sulphur dioxide.
ii) sulphur trioxide.
b) Nitrogen in i) nitrogen monoxide
ii) nitrogen dioxide.
iii) dinitrogen oxide.
iv) dinitrogen pent.
c) Copper in i) cupric oxide.
ii) cuprous oxide.
D1) Complete the table given below for the step by step writing of a formula of a chemical compound. ( The first example has been completed for you)
1) Cr³⁺ SO₄²⁻
Cr₂ (SO₄)₃
Cr₂(SO₄)₃ = Chromium sulphate
2) Mg Cl
3) Na ClO₃
4) K ZnO₂
5) Ca PO₄
6) NH₄ SO₄
7) Na HSO₃
8) Al S
9) Zn SO₄
10) Mg O₄
D2) Give the formulas of the following compounds whose metallic radical exhibits variable valency.
Compound
a) cupric nitrate.
b) Cuprous chloride.
c) Iron(II) sulphate.
d) Mercuric nitrate.
e) Plumbous chloride.
f) Stannous cloride.
g) Mangannic sulphate .
h) Platinic chloride.
i) Mercurous chloride.
j) Iron(III) nitrate.
D3) Give the names of the compounds whose formulas are listed below.
a) HNI₂
b) HCO₃
c) H₂C₂I₄
d) H₃PO₄
e) CH₃COOH
All the above are acids
f) Al(OH)₃
g) CaSiO₃
h) Na₂ZnO₂
i) K₂CrO₄
j) Mg₃N₂.
E1) A chemical equation is a shorthand form for a chemical change
a) 2KClO₃ ---∆--> 2KCl+ 3O₂
i) In the above reaction name the reactant and the products.
ii) State what the arrow in between indicates.
E2) Give reasons for the following :
a) All equations must be balanced.
b) A chemical equation provides useful information about a reaction.
c) All chemical equations have their limitations .
E3) Balance the equation:
a) CuO+ NH₃ ---> Cu+ H₂O+ N₂
b) NH₃ + Cl₂ ----> HCl + NCl₃.
c) Mg₃N₂ + H₂O---> Mg(OH)₂+ NH₃.
d) Pb₃O₄ + HCl ---> PbCl₂ + H₂O + Cl₂.
e) Manganese(IV)+ Hydrochloric ---> Manganese (II)oxide+ Water + Chlorine.
f) Potassium hydroxide + Chlorine ---> Potassium chloride + Potassium hypochlorite + water.
g) Ammonium dichromate ---> Chromium oxide + Water + Nitrogen.
h) Potassium sulphite + Nitric acid ---> Potassium nitrate + Water + Sulphur dioxide.
i) Iron (III) chloride(ferric chloride)+ Water + Sulphur dioxide---> Iron (II) chloride + Sulphuric acid+ Hydrochloric acid.
j) Copper + Sulphuric acid ---> Copper sulphate+ Water + Sulphur dioxide.
k) Iron(III) oxide (ferric oxide)+ Carbon monoxide---> Iron + Carbon dioxide.
l) Sodium sulphite + Sulphuric acid --> Sodium sulphate + Water + Sulphur dioxide.
m) Zinc+ Sodium hydroxide---> Sodium zincate+ Hydrogen.
n) Aluminium+ Carbon dioxide ---> Aluminium oxide+ Carbon.
o) Sodium bicarbonate+ Aluminium sulphate ---> Sodium sulphate + Aluminium hydroxide + Carbon dioxide.
p) Calcium hydroxide + Ammonium sulphate ---> Calcium sulphate + Water + Ammonia.
q) Nitric acid + Magnesium carbonate ---> Magnesium nitrate + Water + Carbon dioxide.
r) Iron(III) oxide + Sulphuric acid ---> Iron (III) Sulphate+ Water .
s) Zinc sulphide + Oxygen ----> Zinc oxide + Sulphur dioxide.
t) Carbon + Nitric acid ---> Carbon dioxide+ Water + Nitrogen dioxide.
E4) Match the Columns
Column - 1
a) A chemical reaction in which two or more elements or compounds react to form one new compound as a product.
b) A chemical reaction in which a chemical compound decomposes or split up into two or more simpler substances. It is generally brought about by heat.
c) A chemical reaction which takes place when an element (of radical) has replaced another element in a compound.
d) A chemical reaction in which two reactants are both decomposed to form new substances by exchanging their radicals.
e) A chemical reaction which employs a catalyst to alter the rate of a reaction.
f) A chemical reaction in which the product formed react together to form the original reactants depending on the conditions of the reaction.
g) A reaction in which a substance dissociates in two two or more simpler substances on application of heat and is a reversible reaction.
h) A reaction which involves addition of oxygen or electronegative element or removal of hydrogen or electropositive element.
i) A reaction which involves addition of hydrogen or electropositive element or removal of oxygen or electronegative element.
j) A chemical reaction which proceeds with evolution of heat energy.
k) A chemical reaction which proceeds with absorption of heat energy.
l) A chemical reaction which proceeds with absorption of light energy.
Column II
i) double decomposition
ii) exothermic reaction
iii) reversible reaction
iv) Displacement reaction
v) combination or synthesis.
vi) Decomposition reaction
vii) thermal dissociation
viii) endothermic reaction
ix) catalytic reaction
x) Oxidation reaction
xi) photochemical reaction.
xii) reduction reaction.
E5) Name the type of reaction of following :
a) additional of zinc to copper sulphate solution.
b) heat on lead nitrate crystals .
c) preparation of oxygen from Potassium chlorate .
d) Conversion of ferrous chloride to ferric chloride using chlorine.
e) formation of ammonia from nitrogen and hydrogen.
f) liberation of hydrogen at the cathode from acidified water.
g) manufacture of glucose by green plants.
h) formation of nitric oxide from nitrogen and oxygen.
i) Addition of zinc to dilute sulphuric acid.
j) NH₄Cl <=> NH₃ + HCl.
k) 2KNO₃ ∆--> 2KNO₂ + O₂.
l) 2H₂O₂ ---ᴴ³ᴾᴼ⁴---> 2H₂O+ O₂.
m) PbBr₂ ---> Pb²⁺ + 2Br¹⁻ (ions).
n) 2HgO ∆---> 2Hg+ O₂.
o) N₂O₄ ∆<=> 2NO₂
p) AgNO₃ + KCl ---> AgCl + KNO₃.
q) Fe + S ----> FeS.
r) H₂ + Cl₂---(sunlight)___> 2HCl.
s) C + H₂O ---> CO + H₂ - ∆
t) Cl₂ + 2KI ---> 2KCl + I₂.
u) 3Fe + 4H₂O <=∆> Fe₃O₄ + 4H₂.
v) 2Cu + O₂ ---> 2CuO.
w) Fe₂O₃ + 2Al ---> Al₂O₃ + 2Fe.
x) KNO₃ + H₂SO₄ ---> HNO₃ + KHSO₄.
y) 2FeCl₂ + Cl₂ ---> 2FeCl₃.
z) Fe+ H₂SO₄---> FeSO₄ + H₂.
A') SO₂ + Cl₂---> SO₂Cl₂.
B') 3Ca + N₂ ---> Ca₃N₂.
C') CuSO₄ + Fe ---> FeSO₄ + Cu.
D') 4HNO₃ ---> 2H₂O+ 4NO₂ + O₂.
E7) From the following Oxidation reaction, find the reducing agent:
a) Cu+ O₂ ---> 2CuO.
b) H₂S+ Cl₂ ---> S + 2HCl.
c) 2FeCl₂+ Cl₂---> 2FeCl₃.
d) SO₂+ H₂O+ Cl₂---> H₂SO₄ + 2HCl.
e) H₂S + 2FeCl₃---> 2FeCl₂ + 2HCl + S.
f) Zn + H₂SO₄---> ZnSO₄ + H₂.
g) Fe + S --- FeS.
h) 2Mg + SO₂----> 2MgO + S.
i) 2H₂S + SO₂---> 3S + 2H₂O.
j) S + 2H₂SO₄----> 3SO₂ + 2H₂O.
From the following Reduction reaction, find the oxidizing agent.
a) CuO+ H₂---> Cu+ H₂O.
b) Br₂ + H₂S---> 2HBr + S.
c) 2FeCl₃ + H₂S ---> 2FeCl₂ + 2HCl + S.
d) 2HgCl₂ + SnCl₂ ---> Hg₂Cl₂+ SnCl₄.
e) 2FeCl₃ + SO₂ + 2H₂O---> 2FeCl₂+ 2HCl+ H₂SO₄.
f) Fe₂(SO₄)₃ + 2H₂O + SO₂ ---> 2FeSO₄ + 2H₂SO₄.
g) Cl₂ + 2H₂O + SO₂ ---> 2HCl + H₂SO₄.
h) 2HNO₃ + SO₂ ---> 2NO₂ + H₂SO₄.
i) 2KMnO₄ + 2H₂O + 5SO₂ ---> 2MnSO₄ + K₂SO₄+ H₂SO₄.
j) K₂Cr₂O₇ + H₂SO₄ + 3SO₂ ---> Cr₂(SO₄)₃+ K₂SO₄ + H₂O.
E8) Name the following:
a) A coloured gaseous oxidising agent.
b) A liquid oxidising agent which on thermal decomposition in presence of a catalyst liberates oxygen.
c) A gaseous reducing agent containing Oxygen.
d) An acid other than nitric and Sulphuric Acid which is an oxidising agent.
e) A gaseous reducing agent neutral in nature other than carbon monoxide.
f) An oxidizing agent which liberates chlorine on heating with concentrating hydrochloric acid.
g) Two neutral gases which react to give a basic gas and the reaction is exothermic.
h) Two neutral gases which react to give a neutral oxide and the reaction is exothermic.
i) A substance which decomposes by absorption of sound energy.
j) Two substances which react explosively on close physical contact.
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