Page 62 - Chemistry ICSE Class X
P. 62
50 ICSE Chemistry – 10
17. Giving two examples, explain the electronic concept of oxidation and reduction.
18. In which part of the periodic table the elements which act (a) as reducing agents, and (b) as oxidising agents, are
located?
19. Why are the electrovalencies of calcium (Ca), aluminium (Al), and oxygen (O) 2+, 3+ and 2–, respectively?
20. A metal X (atomic no. 19) burns in chlorine to produce a white, solid compound Y. By means of diagrams,
illustrate the arrangement of electrons in X, both before and after the reaction.
21. Why do two atoms of argon not form a covalent bond to give an argon molecule?
22. An element A has four electrons in the outermost shell of its atom and combines with another element B having
seven electrons in the outermost shell of its atom. The compound does not conduct electric current and fails to
give a precipitate with a solution of AgNO . What is the nature of the chemical bonds in the compound? Write
3
the electron dot structure of its molecule.
23. Why is it incorrect to talk of the molecules of sodium chloride, but correct to talk of the molecules of ammonia?
24. Sodium chloride is an ionic compound, while hydrogen chloride is a covalent compound. But, both form ions in
their aqueous solutions. Explain how does it happen?
25. Tick (9) the correct answer.
(i) The bond formed between the two atoms of the same element to form a molecule is
(a) ionic
(b) covalent
(c) polar
(d) coordinate
(ii) The number of single covalent bonds present in C H molecule are
2
2
(a) 2
(b) 5
(c) 3
(d) 4
(iii) The number of electrons shared by the atoms of oxygen during the formation of oxygen molecule are
(a) 2
(b) 4
(c) 8
(d) 6
(iv) The chemical formula of aluminium sulphate is
(a) AlSO
4
(b) Al(SO )
4 3
(c) Al (SO )
2 4 3
(d) Al SO
3
4
X /CVEJ VJG V[RG QH DQPF CUUQEKCVGF YKVJ GCEJ QH VJG HQNNQYKPI YJGTG C UVCPFU HQT KQPKE D HQT EQXCNGPV CPF
(c) for coordinate covalent bond.
I. Calcium chloride (a) (b) (c)
II. Hydrogen chloride gas (a) (b) (c)
III. Hydrogen (a) (b) (c)
IV. Magnesium sulphate (a) (b) (c)
V. Urea (a) (b) (c) 
