1993 - JAMB Chemistry Past Questions and Answers - page 2
11
The air around a petroleum refinery is most likely to contain?
A
CO2, SO3 and N2O
B
CO2, CO and N2O
C
SO2, CO and NO2
D
PH3 H2O and CO2
12
Water can be identified by the use of?
A
anhydrous copper (II) tetraoxosulphate (VI)
B
anhydrous sodium trioxocarbonate (IV)
C
potassium heptaoxochromate (VII)
D
copper (II) trioxocaronate (IV)
13
The phenomenon whereby sodium trioxocarbonate (IV) decahydrate loses some of its water of crystallization on exposure to the atmosphere is known as?
A
deliquescene
B
hygroscopy
C
effervescence
D
efflorescence
14
A student prepares 0.5 M solution each of hydrochloric and ethanoic acids and then measured pH. The result would show that the?
A
pH values are equal
B
HCI solution has a higher pH
C
sum of the values is 14
D
ethanoic acid solution has a higher pH
correct option: d
Users' Answers & Comments15
NH3 + H3O+
→ NH4+ + H2O. It may be deduced from the reaction above that?
→ NH4+ + H2O. It may be deduced from the reaction above that?
A
a redox reaction has occurred
B
H3O+ acts as an oxidizing agent
C
H3O+ acts as an acid
D
water acts as ab acid
correct option: c
Users' Answers & Comments16
4.0 g of sodium hydroxide in 250 cm3 of solution contains?
A
0.40 moles per dm3
B
0.10 moles per dm3
C
0.04 moles per dm3
D
0.02 moles per dm3
correct option: a
Unit of concentration = (moles)/(dm3)
If 250 cm3 solution NaOH contains 4.0 g NaOH
i.e -1cm3 solution NaOH (4.0)/(250) g
∴ 1000 cm3 (1 dm3) will contain (40 x 1000) / (250 x 1) = 16 g/dm3
16 g/dm3 = 16g/dm3 + molar mass NaOH
because no of moles = (mass of substance given) / (molar mass)
∴ (16 g) / (40 g) dm3 = (16 g)/(dm3 x (1 mole)/ (40g) = 0.4 (moles)/(dm3)
Users' Answers & CommentsIf 250 cm3 solution NaOH contains 4.0 g NaOH
i.e -1cm3 solution NaOH (4.0)/(250) g
∴ 1000 cm3 (1 dm3) will contain (40 x 1000) / (250 x 1) = 16 g/dm3
16 g/dm3 = 16g/dm3 + molar mass NaOH
because no of moles = (mass of substance given) / (molar mass)
∴ (16 g) / (40 g) dm3 = (16 g)/(dm3 x (1 mole)/ (40g) = 0.4 (moles)/(dm3)
17
During the electrolysis of a salt of a metal M, a current of 0.5 A flows from for 32 minutes 10 seconds and deposits 0.325 g of M, What is the charge of the metal ion?
(M = 65, If = 96,500 C per mole of electron)
(M = 65, If = 96,500 C per mole of electron)
A
1
B
2
C
3
D
4
correct option: b
Ampere = (Coulomb) x (Sec) x 1930 secs = 965 coulombs (unit of current)
But quantity of electricity = current x time = (Coulomb)/(Sec) x time
If 0.5 A for 32 mins 10 secs; Quantity of electricity = (0.5 coulomb)/(Sec x 1930) secs
= 965 coulombs
Since 965 coulombs give 0.325 g M
i.e1 coulombs = (0.325)/(965) g
∴96500 coulombs = (0.30)/(965) x 96500 =32.5 g
∴(65 g)/(32.5) = 2
inference: it takes 2 Faraday of electricity to deposit 1 mole of M. Therefore, the change on M ion = 2.
Users' Answers & CommentsBut quantity of electricity = current x time = (Coulomb)/(Sec) x time
If 0.5 A for 32 mins 10 secs; Quantity of electricity = (0.5 coulomb)/(Sec x 1930) secs
= 965 coulombs
Since 965 coulombs give 0.325 g M
i.e1 coulombs = (0.325)/(965) g
∴96500 coulombs = (0.30)/(965) x 96500 =32.5 g
∴(65 g)/(32.5) = 2
inference: it takes 2 Faraday of electricity to deposit 1 mole of M. Therefore, the change on M ion = 2.
18
Which of the reactions occurs at the anode during the electrolysis of a very dilute aqueous solution of sodium chloride?
A
OH- - e → OH
B
CIsup>-
C
[]
D
[]
correct option: a
Users' Answers & Comments19
The oxidation states of chlorine in HOCL, HCLO3 and HCLO4 are respectively?
A
-1, +5, and +7
B
-1, -5 and 7
C
+1, +3 and +4
D
+1, +5 and +7
correct option: d
Users' Answers & Comments20
A reaction takes places spontaneously if?
A
∆G = O
B
∆S < O and ∆H > O
C
∆H < T ∆S
D
∆G > O
correct option: c
Users' Answers & Comments