Question 1.
Explain the term ‘symbol’. State a reason why – the symbol of calcium
is ‘Ca’ & of copper is ‘Cu’.
Question 2.
Define the term ‘valency’. With reference to water & ammonia as
compounds respectively, state the valency of oxygen & nitrogen.
Magnesium [2, 8, 2] has valency 2+. Give reasons.
Question 3.
Explain the term ‘variable valency‘ Copper having electronic
configuration 2, 8,18,1 exhibits variable valency. Give a reason for the
same & name the compound CuCl & CuCl2.
Question 4.
State the valencies of the following metallic elements –
(a) Potassium
(b) Sodium
(c) Calcium
(d) Magnesium
(e) Zinc
(f) Aluminium
(g) Chromium
[write each symbol with the valency.
Question 5.
Certain metals exhibit variable valencies which include valencies: 1 +,
2+, 3+ & 4+. State the variable valency of the following metals –
(a) Copper
(b) Silver
(c) Mercury
(d) Iron
(e) tin
(f) Lead
[write each symbol with the variable valency]
Question 6.
State which of the following ions or radicals given below of non-
metallic elements exhibit-valency: 1–, 2– & 3–
(a) Chloride
(b) Bromide
(c) Iodide
(d) Nitrate
(e) Hydroxide
(f) Bicarbonate
(g) Bisulphite
(h) Bisulphate
(i) Aluminate
(j) Permanganate
(k) Oxide
(l) Sulphide
(m) Sulphite
(n) Sulphate
(o) Carbonate
(p) Dichromate
(q) Zincate
(r) Plumbite
(s) Phosphate
(t) Nitride
[write each ion or radical with the correct valency]
Question 7.
Differentiate between the terms – ‘Ion’ & ‘radical’ with suitable
examples.
Question 8.
Write the chemical formula of the following compounds in a step-by-
step manner –
(a) Potassium chloride
(b) Sodium bromide
(c) Potassium nitrate
(d) Calcium hydroxide
(e) Calcium bicarbonate
(f) Sodium bisulphate
(g) Potassium sulphate
(h) Zinc hydroxide
(i) Potassium permanganate
(j) Potassium dichromate
(k) Aluminium hydroxide
(l) Magnesium nitride
(m) Sodium zincate
(n) Copper [II] oxide
(o) Copper [I] sulphide
(p) Iron [III] chloride
(q) Iron [II] hydroxide
(r) Iron [III] sulphide
(s) Iron [III] oxide.
Question 9.
What is a chemical equation. How is it represented. Differentiate
between a ‘word equation’ and a ‘molecular equation’ with a suitable
example.
Question 10.
State the information provided by a chemical equation.
Chemical equations suffer from a number of limitations.
State the main limitations of a chemical equation.
Question 11.
State what is a balanced equation with a relevant example.
Give a reason why an equation is balanced with reference to the law of
conservation of matter.
Question 12.
Write balanced molecular equations for the following word equations :
(a) Calcium + oxygen → Calcium oxide
(b) Calcium + water → Calcium + hydrogen
(c) Zinc + sulphuric hydroxide → Zinc sulphate + hydrogen
(d) Lead sulphate acid + ammonium hydroxide → Ammonium sulphate
+ lead hydroxide
(e) Copper hydroxide + nitric acid → Copper nitrate + water
(f) Lead nitrate + sodium Chloride → Sodium nitrate + lead Chloride.
Question 13.
Balance the following equations :
(a) P + O2 → P2 O5
(b) Na2O + H2O → NaOH
(d) Fe + H2O ⇌ Fe3O4 + H2
(c) K + H2O → KOH + H2
(e) CaO + HCl2 → CaCl2 + H2O
(f) Fe + Cl → FeCl3
(g) Al + H3O → Al3O2 + H2
(h) Al + H2SO4 → Al2(SO4)4+ H2
(i) Fe2O3 + H2 → Fe + H2O
(j) C + H2SO4 → CO2 + H2O + SO2
(k) Pb3O4 → PbO + O2
(l) Al + O2 → Al2O3
(m) NO + O2 → NO2
(n) ZnS + O2 → ZnO + SO2
(o) Pb3O4 + HCl →PbCl2 + H2O + Cl2
(p) ZnO + NaOH → Na2ZnO2 + H2O
(q) H2S + Cl2 → S + HCl
(r) FeCI3+ NaOH →NaCl + Fe(OH)3
(s) Fe2 O2 + CO → Fe + CO2
(t) KHCO3 → K2 CO3 + H2 O + CO2
(u) CuO + NH3 → Cu + H2O + N2
Objective Type Questions
Question 1.
Complete the statements given below by filling in the blank with the
correct words.
1. The formula of silver [I] chloride is ……….. [AgCl/AgCl2].
2. The basic unit of an element is a/an ……….. [molecule/ atom/ion]
3. Atoms contains ……….. [netron/nucleus/, with positively charged
………. [electrons/protons].
4. Element ……….. [calcium/lead/carbon] has the symbol derived
from its Latin name ‘plumbum’.
5. From the elements – He, Br, Pt & O; the element which forms a
polyatomic molecule is ……….. & which is liquid
at room temperature is …………
6. The valency of iron in FeO is ……….. [2+/l+] chlorine [chloride] in
CaCl2 is ……….. [l–/2–] and of dichromate in K2Cr2O7is …………
[2+/2–]
Question 2.
Match the statements – 1 to 10 below with their correct . ‘
answers from – A to J.
1. Elements having valency of two – J: K 1+
2. An anion – B: Divalent
3. A gaseous non-metal – C: Reactants
4. A cation – D: Ammonium
5. The term used for the substances which take part in the
chemical reaction – E: Nitric oxide
6. The meaning of the symbol ‘A’ over the arrow in a chemical
equation – F: Nitrogen
7. The chemical name for nitrogen monoxide – G: Zero
8. A radical containing nitrogen & hydrogen only – H: Nitrous
oxide
9. The chemical name for dinitrogen oxide – I: Heat required
10. The valency of noble gases – J: K1+
Question 3.
Match the compounds in List I – 1 to 20 with their correct
formulas in List II – A to T.
1. Copper [I] sulphide – A. KMnO4
2. Potassium permanganate – B. Mg3N2
3. Phosphoric acid – C. Mg(NO3)2
4. Copper [I] oxide – D. Al2(SO4)3
5. Carbonic acid – E. Na2ZnO2
6. Aluminium sulphide – F. N2O
7. Iron [II] oxide – G H2CO3
8. Iron [III] sulphide – H. Al2S3
9. Iron [II] sulphate – I. NO
10. Sodium zincate – J. FeS
11. Nitrous oxide – K. Fe2S3
12. Aluminium sulphate – L. H3PO4
13. Magnesium nitride – M. Cu2S
14. Iron [III] sulphate – N. CuS
15. Copper [II] oxide – O. Fe2O3
16. Iron [III] oxide – P. FeO
17. Nitric oxide – Q. FeSO4
18. Copper [II] sulphide – R. Fe2(SO4)3
19. Iron [II] sulphide – S. CuO
20. Magnesium nitrate – T. Cu2O
