2017 - JAMB Chemistry Past Questions and Answers - page 3
21
\(^{226}_{88}Ra\) → \(^x_{86}Rn\) + alpha particle
A
226
B
220
C
227
D
222
correct option: d
\(^{226}_{88}Ra\) → \(^x_{86}Rn\) + \(^4_{2}He\)
\(^4_{2}He\) = alpha particle
considering the summation of the mass number
226 = x + 4
x = 226 + 4
x = 222
Users' Answers & Comments\(^4_{2}He\) = alpha particle
considering the summation of the mass number
226 = x + 4
x = 226 + 4
x = 222
22
The shape of ammonia molecules is
A
trigonal planar
B
octahedral
C
square planar
D
tetrahedral
23
The mass of silver deposited when a current of 10A is passed through a solution of silver salt for 4830s is – (Ag = 108 F = 96500(mol-1)
A
54.0g
B
27.0g
C
13.5g
D
108.0g
correct option: a
Recall that
m = \(\frac{MmIt}{96500n}\)
Mm =108, t = 4830s
I = 10A, n = 1
m = 108 × 10 × (\(\frac{4830}{96500}\)) × 1
m = 54.0g
Mass deposited = Mm × \(\frac{It}{96500n}\)
Users' Answers & Commentsm = \(\frac{MmIt}{96500n}\)
Mm =108, t = 4830s
I = 10A, n = 1
m = 108 × 10 × (\(\frac{4830}{96500}\)) × 1
m = 54.0g
Mass deposited = Mm × \(\frac{It}{96500n}\)
24
Tin is unaffected by air at ordinary temperature due to its
A
Low melting point
B
Weak electropositive character
C
High boiling point
D
White lustrous appearance
correct option: a
Tin has a melting point of 232° which enables it to be unaffected by air at ordinary temperature coupled with the fact that it also helps in making a good metal for alloying.
Tin is relatively unaffected by both water and oxygen at room temperature due to its low melting point. It does not rust, corrode, or react in any other way. This explains one of its major uses: as a coating to protect other metals.
Users' Answers & CommentsTin is relatively unaffected by both water and oxygen at room temperature due to its low melting point. It does not rust, corrode, or react in any other way. This explains one of its major uses: as a coating to protect other metals.
25
Calculate the amount in moles of silver deposited when 9650C of electricty is passed through a solution of silver salt [= 96500 Cmol-1]
A
0.05
B
10.80
C
10.00
D
0.10
correct option: d
m = \(\frac{Mm \times Q}{96500n
}\)
where Q = IT
M = Mm × \(\frac{Q}{96500n}\)
where m = mass
Mm = Molar mass
Q = Quantity of electricity
n = number of change= +1
\(\frac{M}{Mm}\) = mole = \(\frac{mass}{Molarmass}\)
\(\frac{M}{Mm}\) = \(\frac{Q}{96500n}\)
= \(\frac{9650}{96500n}\) × 1
= \(\frac{1}{10}\) = 0.1mol
Users' Answers & Comments}\)
where Q = IT
M = Mm × \(\frac{Q}{96500n}\)
where m = mass
Mm = Molar mass
Q = Quantity of electricity
n = number of change= +1
\(\frac{M}{Mm}\) = mole = \(\frac{mass}{Molarmass}\)
\(\frac{M}{Mm}\) = \(\frac{Q}{96500n}\)
= \(\frac{9650}{96500n}\) × 1
= \(\frac{1}{10}\) = 0.1mol
26
The reaction of halogens in the presence of sunlight is an example of
A
oxidation reaction
B
addition reaction
C
hydrogenation reaction
D
substitution reaction
correct option: d
Alkanes undergoes substitution reaction and it is an example of halogenation substitution reaction.
Reaction of halogen with alkane in the presence of sunlight (ultraviolet) is termed halogenation. Halogenation is an example of substitution reaction. In addition, alkanes only undergo substitution reaction but not addition reaction.
Users' Answers & CommentsReaction of halogen with alkane in the presence of sunlight (ultraviolet) is termed halogenation. Halogenation is an example of substitution reaction. In addition, alkanes only undergo substitution reaction but not addition reaction.
27
The enzyme used in the hydrolysis of starch to dextrin and maltose is
A
amylase
B
diastatse
C
invertase
D
zymase
correct option: b
This is any amylase or a mixture of amylases that converts starch to dextrin and maltose.
Users' Answers & Comments28
The alkyl group is represented by the general formula
A
CnH2n
B
CnH2n − 2
C
CnH2n + 1
D
CnH2n + 2
correct option: c
Alkyl group has the general formula CnH2n + 1.
This formed when one hydrogen is removed from the alkane family. It has the general formula CnH2n + 1
Users' Answers & CommentsThis formed when one hydrogen is removed from the alkane family. It has the general formula CnH2n + 1
29
CH2S(g) + O2(g) → 2Cn + SO2(g)
What is the change in the oxidation number of copper in the reaction?
What is the change in the oxidation number of copper in the reaction?
A
0 to + 2
B
0 to + 1
C
C + 1 to 0
D
+ 2 to + 1
correct option: c
In the reactant;
Cu2S
2 Cu - 2(1) = 0
2 Cu = 2
Cu = \(\frac{2}{2}\)
Cu = +1
In the product, Cu
Cu = O
The oxidation number of Cu in Cu2S and Cu respectively is +1 and 0 respectively
Users' Answers & CommentsCu2S
2 Cu - 2(1) = 0
2 Cu = 2
Cu = \(\frac{2}{2}\)
Cu = +1
In the product, Cu
Cu = O
The oxidation number of Cu in Cu2S and Cu respectively is +1 and 0 respectively
30
A
SO3
B
SO2
C
S
D
H2S
correct option: b
The setup represents the production of sulfur dioxide. And the cylinder marked X is SO2
Users' Answers & Comments