WAEC - Chemistry (2021)

1
The hydrolysis of proteins by diluting mineral acids produces
პასუხი
(C)
amino acids
2
Which of the following oxide causes acid rain?
პასუხი
(D)
NO\(_{2}\)
3
The ratio of carbon atoms of hydrogen atoms in a hydrocarbon is 1:2. If its molecular mass is 56, what is its molecular formula?
პასუხი
(B)
C\(_{4}\)H\(_{8}\)
4
What is the relative molecular mass of the compound below?

[H = 1.0; C = 12.0; O = 16.0]
პასუხი
(B)
136
5
Cathodic protection of metals is based on
პასუხი
(D)
relative tendencies of oxidation
6
If humid air is polluted by chlorine discharged, the air can be restored by sprinkling
პასუხი
(B)
acidified KMnO\(_{4}\)
7

The alkanol represented by the structure above is
პასუხი
(A)
primary and dihydric
8
Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?
პასუხი
(C)
K\(_{2}\)SO\(_{4}\) and BaCl\(_{2}\)
9
Which of the following illustrates the variation of the rate of evolution of gas from a given length of magnesium ribbon (y-axis) with an increase in the concentration of the added (x-axis)?
პასუხი
(A)
I
10
Which of the graphs illustrates the variation of the pH of a given volume of strong acid solution (y-axis) with the volume of strong base titrated against its (x-axis)?
პასუხი
(A)
I
11
Which of the graphs illustrates the variation of the solubility of a salt in water (y-axis), with an increase in temperature (x-axis) if the dissolution process is exothermic?
პასუხი
(D)
IV
12
The formation of ethene from dehydration of ethanol can be described as-------
პასუხი
(B)
an elimination reaction
13
Which of the following gasses is highly soluble in water at room temperature
პასუხი
(A)
ammonia
14
A molecular of phosphorus is
პასუხი
(C)
tetraatomic
15
The most common method of preparing insoluble salts is by
პასუხი
(D)
double decomposition
16
What number of moles of oxygen would exert a pressure of 10 atm at 320 K in an 8.2 dm\(^{2}\) cylinder?

[R = 0.082 atm dm\(^{3}\) mol\(^{-1}\) K\(^{-1}\)]

პასუხი
(C)
3.13
17
The basic property of salts used as drying agents is by?
პასუხი
(C)
hygroscopy
18
What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper(II) ions?
პასუხი
(A)
blue precipitate is formed which is soluble in excess ammonia
19
When CuSO\(_{4(aq)}\) is added to Pb(NO\(_{3}\))\(_{2(aq)}\)--------
პასუხი
(D)
a white precipitate would be formed
20

Consider the structure above

How many carbon atoms does the parent chain contain?
პასუხი
(B)
4
21
Under which conditions of pressure (p) and temperature (T) would the volume of an inflated ballon increase? When
პასუხი
(C)
T is increased and P is decreased
22
The collision between ideal gas molecules are considered to be perfectly elastic because
პასუხი
(A)
they collide without losing energy
23
Elements with high ionization energies would-------
პასუხი
(C)
have high effective nuclear charges
24
Which of the following statements about Group VII elements is correct?
პასუხი
(C)
their reactivity decreases down the group
25
Which of the following cell notations represent the diagram
პასუხი
(D)
A/A\(^{3+}\)/ /B\(^{2+}\)/B
26
Which of the following half reaction equations represent the reaction at the cathode
პასუხი
(B)
B\(^{2+_{(aq)}}\)+2e\(^{-}\) \(\rightarrow\) B\(_{(s)}\)
27
The reactivity of fluorine is high because of
პასუხი
(A)
its high electronegativity
28
How many coulombs of electricity would liberate 1.08g of Ag from a solution of silver salt?

[Ag = 108.0; 1F = 96500 C]
პასუხი
(C)
965 C
29
The Bohr model of the atom proposed the existence of?
პასუხი
(B)
electron shells
30
The 25°C evaporation of a 100 cm\(^{3}\) solution of K\(_{2}\)CO\(_{3}\) to dryness gave 14g of the salt. What is the solubility of K\(_{2}\)CO\(_{3}\) at 25°C? [K\(_{2}\)CO\(_{3}\) = 138]
პასუხი
(C)
1.01 mol dm \(^{-3}\)
31
Student X titrated 25 cm\(^{3}\) of Na\(_{2}\)CO\(^{3}\) with 0.1 mol dm\(^{-3}\) HCI, using methyl orange as indicator. Student Y carried out the same exercise but used phenolphthalein as an indicator. Which of the following statements about the titration is true?
პასუხი
(B)
the titer values obtained from the titration are equal
32
What is the concentration of a solution which contains 0.28g of potassium hydroxide in 100 cm\(^{3}\) of solution [KOH = 56]
პასუხი
(B)
0.05 mol dm\(^{-3}\)
33
What is the empirical formula of a hydrocarbon containing 0.160 moles of carbon and 0.640 moles of hydrogen
პასუხი
(C)
CH\(_{4}\)
34
Which of the following species has the largest ionic radius
პასუხი
(A)
S\(^{2-}\)
35
Which of the following statements is correct about ionization energy? It
პასუხი
(D)
decreases down the group
36
Potassium trioxonitrate (V) can be obtained from its solution by----------
პასუხი
(C)
crystallization
37
An element, Q, contains 69% of\(^{63}\)Q and 31% of \(^{65}\)Q. What is the relative atomic mass of Q?
პასუხი
(B)
63.6
38
The following ions have the same electron configuration except

\(_{8}\)O, \(_{12}\)Mg, \(_{13}\)AI, \(_{17}\)CI
პასუხი
(A)
CI\(^{-}\)
39
The region around the nucleus where electrons can be located is called?
პასუხი
(B)
an orbital
40
Protons and electrons are called fundamental particles because they----------
პასუხი
(D)
are found in all matter
41
The activation energy of the reaction is
პასუხი
(C)
E\(_{C}\)
42

The enthalpy change of the reaction is------------
პასუხი
(D)
E\(_{D}\)
43
The energy profile diagram illustrates-------------
პასუხი
(B)
an exothermic reaction
44
How many molecules of oxygen would occupy a volume of 2.24 cm\(^{3}\) at s.t.p?

[Molar volume at s.t.p = 22,400 cm\(^{3}\), Avogadro's number = 6.02 x 10\(^{23}\)]
პასუხი
(C)
6.02 x 10\(^{19}\)
45
The isotopes of neon are represented by the symbols \(^{20}\)\(_{x}\) Ne, \(^{21}\) \(_{y}\) Ne, and \(^{22}\) \(_{z}\) Ne. The relationship between x, y, and z is?
პასუხი
(C)
x = y= z