WAEC - Chemistry (2021)

1
The hydrolysis of proteins by diluting mineral acids produces
Відповідь
(C)
amino acids
2
Which of the following oxide causes acid rain?
Відповідь
(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?
Відповідь
(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]
Відповідь
(B)
136
5
Cathodic protection of metals is based on
Відповідь
(D)
relative tendencies of oxidation
6
If humid air is polluted by chlorine discharged, the air can be restored by sprinkling
Відповідь
(B)
acidified KMnO\(_{4}\)
7

The alkanol represented by the structure above is
Відповідь
(A)
primary and dihydric
8
Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?
Відповідь
(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)?
Відповідь
(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)?
Відповідь
(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?
Відповідь
(D)
IV
12
The formation of ethene from dehydration of ethanol can be described as-------
Відповідь
(B)
an elimination reaction
13
Which of the following gasses is highly soluble in water at room temperature
Відповідь
(A)
ammonia
14
A molecular of phosphorus is
Відповідь
(C)
tetraatomic
15
The most common method of preparing insoluble salts is by
Відповідь
(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\(^{-1}\)]

Відповідь
(C)
3.13
17
The basic property of salts used as drying agents is by?
Відповідь
(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?
Відповідь
(A)
blue precipitate is formed which is soluble in excess ammonia
19
When CuSO\(_{4(aq)}\) is added to Pb(NO\(_{3}\))\(_{2(aq)}\)--------
Відповідь
(D)
a white precipitate would be formed
20

Consider the structure above

How many carbon atoms does the parent chain contain?
Відповідь
(B)
4
21
Under which conditions of pressure (p) and temperature (T) would the volume of an inflated ballon increase? When
Відповідь
(C)
T is increased and P is decreased
22
The collision between ideal gas molecules are considered to be perfectly elastic because
Відповідь
(A)
they collide without losing energy
23
Elements with high ionization energies would-------
Відповідь
(C)
have high effective nuclear charges
24
Which of the following statements about Group VII elements is correct?
Відповідь
(C)
their reactivity decreases down the group
25
Which of the following cell notations represent the diagram
Відповідь
(D)
A/A\(^{3+}\)/ /B\(^{2+}\)/B
26
Which of the following half reaction equations represent the reaction at the cathode
Відповідь
(B)
B\(^{2+_{(aq)}}\)+2e\(^{-}\) \(\rightarrow\) B\(_{(s)}\)
27
The reactivity of fluorine is high because of
Відповідь
(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]
Відповідь
(C)
965 C
29
The Bohr model of the atom proposed the existence of?
Відповідь
(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]
Відповідь
(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?
Відповідь
(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]
Відповідь
(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
Відповідь
(C)
CH\(_{4}\)
34
Which of the following species has the largest ionic radius
Відповідь
(A)
S\(^{2-}\)
35
Which of the following statements is correct about ionization energy? It
Відповідь
(D)
decreases down the group
36
Potassium trioxonitrate (V) can be obtained from its solution by----------
Відповідь
(C)
crystallization
37
An element, Q, contains 69% of\(^{63}\)Q and 31% of \(^{65}\)Q. What is the relative atomic mass of Q?
Відповідь
(B)
63.6
38
The following ions have the same electron configuration except

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

The enthalpy change of the reaction is------------
Відповідь
(D)
E\(_{D}\)
43
The energy profile diagram illustrates-------------
Відповідь
(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\(^{23}\)]
Відповідь
(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?
Відповідь
(C)
x = y= z