## Chemistry Study Mode

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Question 1 Chemistry | WAEC/GCE (2017)
A
Electron
B
Neutron
C
Nucleus
D
Proton
Explanation.

An element's chemical properties depend on its valence electrons.The chemical properties of elements depend on an element's electron configuration.

Question 2 Chemistry | WAEC/GCE (2017)
A
B
pipette
C
test tube
D
burette
Explanation.

Test tubes are convenient containers for heating small amounts of liquids or solids with a Bunsen burner or alcohol burner.

Question 3 Chemistry | WAEC/GCE (2017)
A
quantity of electrons in the valence shell
B
filling the orbitals with lower energy first
C
the filling of degenerated orbitals
D
quantum numbers of electrons
Explanation.

Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers.

Question 4 Chemistry | WAEC/GCE (2017)
A
$$Zn^{2+}$$
B
$$Sc^{3+}$$
C
Cu
D
$$Mn$$
Explanation.

Scandium has electronic configuration $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{1}4s^{2}$$ hence, $$Sc^{3+}$$ has configuration $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}$$. Hence, no electron in the 3d-orbital.

Question 5 Chemistry | WAEC/GCE (2017)
A
nitrogen is less dense than oxygen
B
oxygen is more reactive than nitrogen
C
of the difference in their boiling points
D
they belong to the same period
Explanation.

The various gases vaporize as their boiling points are reached, then they are pumped away and separately re-liquefied for convenient storage.

Question 6 Chemistry | WAEC/GCE (2017)
A
boiling point
B
melting point
C
conductivity
D
solubility
Explanation.

The purity of a solid can be determined by measuring the melting point. A pure solid will have a single, sharp melting point.

Question 7 Chemistry | WAEC/GCE (2017)
A
66.0g
B
76.0g
C
80.0g
D
96.0g
Explanation.

This is same as asking for the molar mass of the compound

= $$(2\times 14.0)+ (8\times 1.0) + 12.0+(16.0\times 3)$$

= 28.0+8.0+12.0+48.0 = 96.0g

Question 8 Chemistry | WAEC/GCE (2017)
A
the circular path through which electrons revolve round the nucleus
B
a region around the nucleus where electrons are most likely to be found
C
the path around the nucleus through which electrons move
D
the path around the nucleus through which protons move
Explanation.

The orbital is a path or region around the nucleus. The electrons move in the orbitals and not through it.

Question 9 Chemistry | WAEC/GCE (2017)
A
electronegativity
B
electron affinity
C
D
ionization energy
Explanation.

The ionic radius decreases across a period but increases along a group.

Question 10 Chemistry | WAEC/GCE (2017)
A
nuclear charge increases while the outermost electrons are drawn closer to the nucleus
B
nuclear charge decreases while the outermost electrons are drawn closer to the nucleus
C
valence electrons increase across the period while the valence shell remains constant
D
nuclear charge decreases while the distance of the valence shell from the nucleus is increasing
Explanation.

This is caused by the increase in the number of protons and electrons across a period.

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