2007 - JAMB Chemistry Past Questions and Answers - page 3
21
Calculate the number of moles of HCl present in 20cm3 of a 0.75M solution of the acid
A
0.015 mole
B
0.038 mole
C
3.800 moles
D
1.500 moles
correct option: a
Number of moles = (conc. in mol/dm3*volume in cm3)/1000
(0.75 * 20)/100 = 0.015 mole
Users' Answers & Comments(0.75 * 20)/100 = 0.015 mole
22
The oxidation state of oxygen in tetraoxosulphate (VI) acid is
A
-4
B
-2
C
+4
D
-8
correct option: b
H2SO4
(O.N of hydrogen * 2 ) + O.N of sulphur + O.N of oxygen * 4 = 0
∴ 1 * 2 + 6 + 4x = 0
2 + 6 + 4x = 0
8 + 4x = 0
4x 0 - 8 = -8
4x = -8
x = -8/4 = -2
Users' Answers & Comments(O.N of hydrogen * 2 ) + O.N of sulphur + O.N of oxygen * 4 = 0
∴ 1 * 2 + 6 + 4x = 0
2 + 6 + 4x = 0
8 + 4x = 0
4x 0 - 8 = -8
4x = -8
x = -8/4 = -2
23
MnO2(s) + xHCl(aq) → MnCl2(aq) + yH2O(l) + zCl2(g)
In theequation above, what are the values of x, y and z respectively
In theequation above, what are the values of x, y and z respectively
A
2, 1, 2
B
4, 1, 2
C
4, 2, 1
D
1, 2, 1
correct option: c
Users' Answers & Comments24
Calculate the mass of chlorine gas which occupies a volume of 1.12dm3 at s.t.p
[Cl = 35.5, molar volume of gas at s.t.p = 22.4 dm3
[Cl = 35.5, molar volume of gas at s.t.p = 22.4 dm3
A
15.50 g
B
7.10 g
C
3.55 g
D
1.80 g
correct option: c
2 * 35.5g of chlorine has a volume of 22.4 dm3 at s.t.p
∴ xg of chlorine will have a volume of 1.12 dm3
x = (1.12 * 35.5 * 2)/22.4 = 3.55g
Users' Answers & Comments∴ xg of chlorine will have a volume of 1.12 dm3
x = (1.12 * 35.5 * 2)/22.4 = 3.55g
25
Which experiment led to the measurement of the charge on an electron?
A
Mass spectrometric experiment
B
Oil-drop experiment
C
Scattering α - particles
D
Discharge-tube experiment
correct option: b
Users' Answers & Comments26
What is the volume of oxygen required to burn complete 45 cm3 of methane at s.t.p?
A
135.0 cm3
B
180.0 cm3
C
45.0 cm3
D
90.0 cm3
correct option: d
CH4(g) + 2O2(g) → 2H2O(g) + CO(g)
1 volume of methane will react with 90 cm3 of oxygen at s.t.p
Users' Answers & Comments1 volume of methane will react with 90 cm3 of oxygen at s.t.p
27
How many electrons are in the L shell of 3115P?
A
5
B
8
C
18
D
2
correct option: b
Users' Answers & Comments28
If the electron configuration of a element is p1s2 2s2 2P5, how many unpaired electron are there?
A
2
B
8
C
1
D
4
correct option: c
Users' Answers & Comments29
Which of the following decrease when a given mass of gas is compressed to half its initial volume?
A
Atomic radius of each
B
Average intermolecular distance
C
Frequency of collisions
D
Number of molecules presents
correct option: b
Users' Answers & Comments30
the elements that belong to the third period of the periodic table are
A
Li, Be, Al and P
B
Na, P, O and Cl
C
B, C, N and O
D
Nz, Mg, S and Ar
correct option: d
Users' Answers & Comments