## Chemistry 2018 Study Mode

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Question 1 Chemistry 2018 | WAEC/GCE (2018)
A
Ethene
B
Methane
C
Sulphur
D
Hydrogen
Explanation.

Ethene is the most important organic chemical, by weight, that is manufactured. It is an important raw material for the production of plastics and antifreeze solutions as well as solvents.

Question 2 Chemistry 2018 | WAEC/GCE (2018)
A
Pentane
B
Benzene
C
Propane
D
Hexane
Explanation.

An example of benzene addition reaction is the formation of cyclohexane by a mix of benzene vapour and hydrogen passed over nickel catalyst; while chlorobenzene is formed by substitution reaction.

Question 3 Chemistry 2018 | WAEC/GCE (2018)
A
$$HNO_{{3}{(aq)}} + NaOH_{(aq)} \to NaNO_{{3}{(aq)}} + H_{2}O_{(l)}$$
B
$$AgNO_{{3}{(aq)}}+KCl_{(aq)} \to AgCl_{(s)}+KNO_{{3}{(aq)}}$$
C
$$CaCO_{{3}{(s)}} \to CaO_{(s)} + CO_{{2}{(g)}}$$
D
$$2H_{2}S_{(s)} + SO_{{2}{(g)}} \to 2HO_{2} + 3S_{(g)}$$
Explanation.

No official Explanation yet!

Question 4 Chemistry 2018 | WAEC/GCE (2018)
A
decomposition
B
oxidation
C
reduction
D
sublimation
Explanation.

The Iron is to to be gotten by the removal of oxygen from its ore, and this is called a reduction reaction.

Question 5 Chemistry 2018 | WAEC/GCE (2018)
A
0.08$$gdm^{-3}$$
B
2.00$$gdm^{-3}$$
C
8.00$$gdm^{-3}$$
D
80.00$$gdm^{-3}$$
Explanation.

1000$$cm^{3}$$ = 1$$dm^{3}$$

200$$cm^{3}$$ = 0.2$$dm^{3}$$

⇒ 0.2$$dm^{3}$$ contains 0.4g

hence, solubility of the salt which is the amount of the salt dissolvable in 1$$dm^{3}$$ is

$$\frac{0.4g}{0.2dm^{3}} = 2.0gdm^{-3}$$

Question 6 Chemistry 2018 | WAEC/GCE (2018)
A
double anions in its aqueous solution
B
a single cation in its aqueous solution
C
hydrogen ions in its aqueous solution
D
hydrogen atoms in its aqueous solution
Explanation.

Acid salts are salts whose aqueous solutions are acidic in character, implying that their aqueous solutions possess hydrogen ions.

Question 7 Chemistry 2018 | WAEC/GCE (2018)
A
reaction vessel feels cool during the reaction
B
enthalpy change is negative
C
bond forming energy exceeds bond breaking energy
D
heat of formation of reactants exceeds heat of formation of products
Explanation.

Endothermic reactions absorb heat from their surroundings during the reaction process. This means that in the course of the reaction the vessel being used in the reaction will be cool in the process.

Question 8 Chemistry 2018 | WAEC/GCE (2018)
A
CH$$_{4}$$
B
HCl
C
NH$$_{3}$$
D
NaH
Explanation.

The bonding between a non-metal and a metal is an ionic bonding. In metal hydrides, Hydrogen takes on the ionic charge of -1, hence forming an ionic bond with the metals.

Question 9 Chemistry 2018 | WAEC/GCE (2018)
A
$$C_{2}H_{4}$$
B
$$C_{3}H_{4}$$
C
$$C_{3}H_{6}$$
D
$$C_{4}H_{8}$$
Explanation.

Given the molecular formula, $$CH_{2}$$.

The empirical formula will be $$(CH_{2})n$$= 42

$$(12+(2\times1))n =42$$

⇒ $$14n =42$$

n = 3, hence the empirical formula is $$C_{3}H_{6}$$

Question 10 Chemistry 2018 | WAEC/GCE (2018)
A
an oxidizing agent
B
a reducing agent
C
an acid
D
a base
Explanation.

No official Explanation yet!

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