12th class (Fsc) Chemistry unit 3 MCQs
26. It causes softening of water by converting calcium and magnesium into:
a. Water soluble hydroxides
b. Water soluble borates
c. Water insoluble hydroxides
d. Water insoluble borates
27. Which is most important and stable boric acid?
a. Tetra boric acid
b. Pyroboric acid
c. Orthoboric acid
d. Meta boric acid
28. The crystalline shape of orthoboric acid is:
a. Trigonal
b. Monocline
c. Ortho-rhombie
d. Tricline
29. The formula of orthoboric is H3BO3 which may be written as:
a. 2B2O3 .3H2O
b. B2O3 .H2O
c. B2O3 .3H2O
d. 2B2O3 .H2O
30. Which one of the following is more reactive metal?
a. Cr
b. Al
c. Fe
d. Zn
31. Which one of following reactions of aluminium is accompanied with evolution of heat and white light?
a. 2AI+N2 → 2AIN
b. 2AI+3H2 → 2AIH3
c. 2AI+3S → AI2S3
d. 2AI+3O2 → 2AI2O3
32. Aluminum and aluminum alloys are does not suitable for marine use due to the fact that:
a. It corrodes badly
b. It is stable metal
c. None of given
d. It is not attacked by ater
33. Aluminum dissolve in dilute acids to form respective salts and a gas evolved which is:
a. H2
b. Cl2
c. H2S
d. SO2
34. Aluminum is not attacked by:
a. Concentrated HNO3
b. Dilute HNO3
c. Hot concentrated HNO3
d. Hot dilute NHO3
35. Aluminum when treated with dilute nitric acid which gas evolved?
a. O2
b. H2
c. No gas evolved
d. NO2
36. Which metal us used in the thermite process because of its activity?
a. Aluminum
b. Iron
c. Zinc
d. Copper
37. When aluminum is react with dilute nitiric acid it produce aluminum nitrate, water and?
a. NO2
b. NO
c. O2
d. NH4 NO3
38. Which gas is evolved when aluminum dissolved in aqueous of alkalies?
a. H2O(g)
b. H2(g)
c. Both H2(g) and O2
d. O2(g)
39. which element is form an ion with charge +3: (A
a. C
b. Be
c. Si
d. Al
40. Silicon is found in earth’s crust up to:
a. 8.5%
b. 3.7%
c. 19%
d. None of these
41. The elements of group IVA are characterized by set of:
a. 6 valence electron
b. 2 valence electron
c. 3 valence electron
d. 4 valence electron
42. The elements of group IVA form hydrides of the type:
a. MH2
b. MH4
c. MH3
d. MH
43. The catenation is characteristic property of;
a. Sn
b. Si
c. pb
d. C
44. Which properties are common between B and Si?
a. High m.p
b. Metalloids
c. Semi-conductor
d. All of these
45. Which of the following elements exhibit allotropy?
a. B and Si
b. AI and Ga
c. Si and Ga
d. None of these
46. Both B and Si form:
a. salt-like hydrides
b. Ionic hydrides
c. polymeric hydrides
d. Covalent hydrides
47. The oxides of B and Si are:
a. Neutral
b. Acidic
c. Amphoteric
d. Basic
48. Opal is a hybrated variety of;
a. Zircon
b. Quartz
c. Asbestos
d. None of these
49. The observed bond distance in C-O in CO2 is:
a. 115pm
b. 105pm
c. 120pm
d. 110pm
50. The molecule of carbon monoxide has a dipole moment:
a. 0.113 D
b. 0.112 D
c. 0.116 D
d. 0.110 D