WAEC CHEMISTRY OBJECTIVE ANSWERS JUNE 2007
1.
C for more understanding click here
2. A
3.C
4.C
5.A
6.B
7.A
8.C
9.B
10.C
11.A
12.A.
13.
250cm3 of distilled water contains 14.8g of salt(z)
1cm3
of distilled water will contain 14.8 X 1 of salt (z)
-----------
250
1000cm3
of distilled water will contain 14.8 X 1000
--------------
250
=
59.2g/dm3 of salt (z)
Concentration in mol/dm3 = Concentration in g/dm3
-------------------------
molar mass
0.80 = 59.2
---------------
molar mass
By cross multiplying we have;
molar mass = 59.2
--------
0.8
molar mass = 74.0 g/mol (D)
14.
One mole of hydrogen gas has 6.02 x 1023 atoms mole concept.
Therefore,
one mole of hydrogen gas will have 6.02 x 1023 atoms (B)
15.
Percentage composition of O2 mass of O2
= --------------------- x 100
molar mass k2cr2O7
= 16 x 7
------------- x 100 = 11200
294 -----------
294
= 38.09% (D)
16.D
17.D
18.D
19.A
20.B
21.
CAVA NA
--------- = -----
CBVB NB
0.8 X 25 1
------------- = ----
CB X 20 1
CB = 0.8 x 25
----------
20
= 1.0
THEREFORE, CB =
1.0 mol/dm3
22.A
23.D
24.C
25.A
26.A
27.C
28.C
29.A
30.A.
31. K2CrO4
(Oxidation number of K) x 2 + Oxidation number of Cr +
(Oxidation number of oxygen) x 4 = 0
Let the oxidation number of cr = x
1 x 2 + x + (-2) x 4 = 0
2 + x + (-8) = 0
2+x-8 = 0
X = 8-2 =
+6 (D) CLICK HERE TO GET MORE INSIGHT
32.B
33.B
34.C
35.
C H
0.08 0.32
------ -----
0.08 0.08
1 : 4
CH4 (C)
36.B
37.D
38.D
39.D
40.B
41.B
42.C
43.A
44.B
45.B
46.B
47.C
48.A
49.A
50.
2g of H2 occupy 22.4 dm3 at S.t.P
1g of H2 will occupy 22.4 dm3 at S.t.P
---------
2
0.5g of H2 will occupy
--------------
2
=
5.60dm3 (B)
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