2015 - JAMB Chemistry Past Questions and Answers - page 6
51
Alloys are best prepared by
A
electroplating
B
Arc-welding
C
reducing and mixture of their metallic
D
cooking a molten of the metals
correct option: d
Alloy is a metal that consist of two or more metals mixed together e.g. is mass which is an alloy of copper and zinc. Are not prepared with option A,B,C, and the do not result in mixture and metals together
Users' Answers & Comments52
In countries where the temperature fall below 273k, salt always spilled on the ray road in order to
A
increase the making point office
B
increase the density of the ice
C
make the ice impure
D
rinse the making point of the ice
correct option: a
Salt is good chemical agent that lowers the melting of an ice only it temperature below 0°C options B,C,D will not have the melting point except is above the 0° C. only salt does that.
Users' Answers & Comments53
What is the volume of energy required to burn 45cm3 of mixture at S.T.P
A
135.0cm3
B
150.0cm3
C
45.0cm3
D
90.0cm3
correct option: d
CH4(g) + 2O2(g) → 2H2O(g)
1 volume of methane will react with 90cm3 of oxygen at S.T.P
Users' Answers & Comments1 volume of methane will react with 90cm3 of oxygen at S.T.P
54
The substance that is used in the steel industry for the removal of carbon. Sulphur and phosphorus impurities from pig iron is
A
oxygen
B
chlorine
C
nitrogen
D
hydrogen
correct option: a
Oxygen is a substance that is used to remove impurities from pig iron. Options B, C, D will be effective in removing impurities positive]
Users' Answers & Comments55
If glucose is heated on the concentration tetraoxosulphate(iv)acid, it will be dehydrated
A
carbon
B
carbon(iv)oxide
C
ethane
D
ethanol
correct option: a
Carbon concentration of 4 will not give a precipitate heating. Option B,C,D will not be dehydrated
Users' Answers & Comments56
Rare gases are suitable because they
A
are monoatomic
B
form ions easily
C
have duplet or octet electronic configuration in the outermost shells in their atoms
D
are volatile gases
correct option: c
Rare gases are stable because they have duplet or octet electronic configurations in the outermost shells in their atoms, as a result they don’t go into solution easily. option A, B, Dare not because they go into solution easily (unstable)
Users' Answers & Comments57
Which of the following compounds can be represented by the molecular formula C2 H6O?
A
propanal
B
ethanol
C
methanoic acid
D
glucose
correct option: b
Ethanol has the molecular formula C2H6O. Option A, C, D are not because their molecular are not different
Users' Answers & Comments58
Two equal bulbs, one containing ammonia and the other one opened mouth-to mouth to each other at temperature the entropy in the mixture of gases is likely to
A
remain unchanged
B
increase
C
decrease
D
charge
correct option: a
The bubble remain the same because entropy favors the mixture as it is the degree of randomness or disorderliness. Option B,C,D will not favors the entropy
Users' Answers & Comments59
what is the pH of 0.00lmoldm3 solution of sodium hydroxide
A
14
B
13
C
12
D
11
correct option: d
[H+][OH−] = 10 − 4
[H+] =10 − 14 ÷ [OH+]
=10 −14 ÷ (1 × 10 − 3) = 10 − 11
pH = − log10[H+ ]
= − log10[10 − 11] = − 1 × −11
log10[10 − 11] = 1
= − 1 × 11 × 1
= − 11
Users' Answers & Comments[H+] =10 − 14 ÷ [OH+]
=10 −14 ÷ (1 × 10 − 3) = 10 − 11
pH = − log10[H+ ]
= − log10[10 − 11] = − 1 × −11
log10[10 − 11] = 1
= − 1 × 11 × 1
= − 11
60
According to the kinetic theory an absence in temperature causes the kinetic energy of particles to
A
decrease
B
increase
C
remain constant
D
be zero
correct option: c
Users' Answers & Comments