Nkojọpọ....






Tẹ mọ́ & Dì mú láti fà yíká.
Tẹ ibi lati pa

JAMB UTME - Chemistry - 2019

Ibeere 1 Ìròyìn

A solution X, on mixing with \( \mathrm{AgNO_3} \) solution gives a white precipitate soluble in aqueous \( \mathrm{NH_3} \), a solution Y, when also added to X, also gives a white precipitate which is soluble when heated solutions X and Y respectively contain

Al

^{3 +}

, Cl

^{-}

Hg

^{+}

, SO

_{4}^{2 -}

Pb

^{2 +}

, Cl

^{-}

Ag

^{+}

, SO

_{4}^{2 -}

Chemistry Of Carbon Compounds (Ghana Only)

Ibeere 8 Ìròyìn

The emission of two successive beta particles from the nucleus \( {}^{32}_{15}\mathrm{P} \) will produce

_{14}^{30}

Si

_{13}^{32}

Al

_{17}^{32}

Cl

_{16}^{32}

S

Awọn alaye Idahun

Explanation:

_{15}^{32}

P

\to

2

_{- 1}^{0}

e +

_{b}^{a}

X
32 = 2(0) + a
a = 32
15 = 2(-1) + b
b = 15 + 2
b = 17

∴

_{b}^{a}

X =

_{17}^{32}

Cl

Ka ìwé ẹ̀kọ́ nípa Structure Of The Atom (WAEC)

Structure Of The Atom

Ibeere 9 Ìròyìn

For the general equation of the nature

XP + yQ ⇌ mR + nS, the expression for the equilibrium constant is

k[P]

^{x}

[Q]

^{y}

\frac{m [R] [S]}{x [P] y [Q]}

\frac{[P]^{x} [Q]^{y}}{[R]^{m} [S]^{n}}

\frac{[R]^{m} [S]^{n}}{[P]^{x} [Q]^{y}}

Awọn alaye Idahun

The expression for the equilibrium constant for the general equation XP + yQ ⇌ mR + nS is: Kc = [R]m[S]n / [P]x[Q]y where Kc is the equilibrium constant, [R] and [S] are the concentrations of the products, and [P] and [Q] are the concentrations of the reactants, all raised to the stoichiometric coefficients (m, n, x, y) in the balanced equation. This equation is known as the equilibrium constant expression and it represents the ratio of the concentrations of the products and reactants at equilibrium for a particular chemical reaction. The equilibrium constant is a measure of how far a reaction proceeds towards completion, with a larger value indicating a greater extent of reaction. The equilibrium constant expression is derived from the law of mass action, which states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants raised to their stoichiometric coefficients. At equilibrium, the rates of the forward and reverse reactions are equal, and the equilibrium constant expression represents the ratio of the rate constants for these two reactions. Therefore, the correct expression for the equilibrium constant for the general equation XP + yQ ⇌ mR + nS is Kc = [R]m[S]n / [P]x[Q]y.

Ka ìwé ẹ̀kọ́ nípa Chemical Kinetics And Equilibrium Systems (Ghana Only) (WAEC)

Ka ìwé ẹ̀kọ́ nípa Chemical Equilibria (JAMB)

Chemical Kinetics And Equilibrium Systems (Ghana Only)

Chemical Equilibria

Ibeere 10 Ìròyìn

X is a substance which liberates \( \mathrm{CO_2} \) on treatment with concentrated \( \mathrm{H_2SO_4} \). A warm solution of X can decolorize acidified \( \mathrm{KMnO_4} \). X is

HCOOH

NaHCO

_{3}

FeCO

_{3}

H

_{2}

C

_{2}

O

_{4}

Awọn alaye Idahun

It should be noted that for X to liberate CO $_{2}$ , X must be a carbonate or an oxalate. Since X decolorizes KMnO $_{4}$ , X must be an oxalate.
Therefore, X is H $_{2}$ C $_{2}$ O $_{4}$ .

Ka ìwé ẹ̀kọ́ nípa Periodic Chemistry (Ghana Only) (WAEC)

Periodic Chemistry (Ghana Only)

Ibeere 11 Ìròyìn

Which of the following reactions is an oxidation process?

2H

^{+}

+ 2e

^{-}

\to

H

_{2}

2O

^{2 -}

+ 4e

^{-}

\to

O

_{2}

OCl

^{-}

+ H

_{2}

O + 2e

^{-}

\to

2OH

^{-}

+ Cl

^{-}

Cl + e

^{-}

\to

Cl

^{-}

Oxidation And Reduction

Ibeere 16 Ìròyìn

The electronic configuration of element Z is \(1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^1\). What is the formula of the compound formed between Z and tetraoxosulphate (VI) ion.

Z

_{3}

(SO

_{4}

)

_{2}

ZSO

_{4}

Z

_{2}

SO

_{4}

Z

_{2}

(SO

_{4}

)

_{3}

Awọn alaye Idahun

Z = 1s $^{2}$ 2s $^{2}$ 2p $^{6}$ 3s $^{2}$ 3p $^{1}$
$∴$ We have Z $^{3 +}$ and SO $_{4}^{2 -}$
The reaction : Z $^{3 +}$ + SO $_{4}^{2 -}$ $\to$ Z $_{2}$ (SO $_{4}$ ) $_{3}$ .

Ka ìwé ẹ̀kọ́ nípa Atomic Structure And Bonding (JAMB)

Atomic Structure And Bonding

Ibeere 17 Ìròyìn

Methane is prepared in the laboratory by heating a mixture of sodium ethanoate with soda lime. The chemical constituent(s) of soda lime is/are

Ca(OH)

_{2}

and NaOH

Na

_{2}

CO

_{3}

NaCl

NaOH

Chemical Combination

Ibeere 18 Ìròyìn

By what amount must the temperature of 200cm\(^{3}\) of Nitrogen at 27°C be increased to double the pressure if the final volume is 150cm\(^{3}\) (Assume ideality)

150°C

177°C

75°C

120°C

Awọn alaye Idahun

Using the ideal gas law and equation:
$\frac{P_{1} V_{1}}{T_{1}} = \frac{P_{2} V_{2}}{T_{2}}$
$\frac{P_{1} \times 200 {cm}^{3}}{300 K} = \frac{2 P \times 150 {cm}^{3}}{T_{2}}$
Cross multiply:
$T_{2} = \frac{300 \times 150 \times 2 P}{200 \times P}$
$= 450 K$ or $177^{\circ} C$
Don't forget to convert to $^{\circ} C$

Ka ìwé ẹ̀kọ́ nípa Kinetic Theory Of Matter And Gas Laws (JAMB)

Kinetic Theory Of Matter And Gas Laws

Ibeere 20 Ìròyìn

At 27°C, 58.5g of sodium chloride is present in 250cm\(^3\) of a solution. The solubility of sodium chloride at this temperature is?

(molar mass of sodium chloride = 111.0gmol\(^{-1}\))

2.0 moldm

^{- 3}

0.25 moldm

^{- 3}

1.0 moldm

^{- 3}

0.5 moldm

^{- 3}

Awọn alaye Idahun

Given the Mass of the salt = 58.5g
Volume = 250 cm $^{3}$ = 0.25 dm $^{3}$
Mass concentration = $\frac{M a s s}{V o l u m e}$
= $\frac{58.5}{0.25}$ = 234 gdm $^{- 3}$
Solubility (in moldm $^{- 3}$ = $\frac{234}{111}$
= 2.11 moldm $^{- 3}$
$≊$ 2.0 moldm $^{- 3}$

Ka ìwé ẹ̀kọ́ nípa Solubility Of Substances (Ghana Only) (WAEC)

Solubility Of Substances (Ghana Only)

Ibeere 21 Ìròyìn

An element Z contains 80% of \( {}^{16}_{8}\mathrm{Z} \) and 20% of \( {}^{18}_{8}\mathrm{Z} \). Its relative atomic mass is

16.2

17.6

16.0

16.4

Awọn alaye Idahun

R.A.M of Z = $16 (\frac{80}{100}) + 18 (\frac{20}{100})$
= $12.8 + 3.6$
= 16.4

Ka ìwé ẹ̀kọ́ nípa Separation Of Mixtures And Purification Of Chemical Substances (JAMB)

Ka ìwé ẹ̀kọ́ nípa Atomic Structure And Bonding (JAMB)

Separation Of Mixtures And Purification Of Chemical Substances

Atomic Structure And Bonding

Ibeere 24 Ìròyìn

When chlorine water is exposed to bright sunlight, the following products are formed

HCl

_{(a q)}

and Cl

_{2}

HOCl

_{(a q)}

and Cl

_{2}

HCl

_{(a q)}

and O

_{2}

HOCl

_{(a q)}

and O

_{2}

Chemistry Of Carbon Compounds (Ghana Only)

Ibeere 26 Ìròyìn

A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180. Find the molecular formula.

[H = 1, C = 12, O = 16]

C

_{3}

H

_{6}

O

_{3}

C

_{6}

H

_{6}

O

_{3}

C

_{6}

H

_{12}

O

_{6}

CH

_{2}

O

Chemistry Of Carbon Compounds (Nigeria Only)

Ibeere 30 Ìròyìn

The following are isoelectronic ions except

Na

^{+}

Mg

^{2 +}

Si

^{2 +}

O

^{2 +}

Awọn alaye Idahun

Two or more ions are said to be isoelectronic if they have the same electronic structure and the same number of valence electrons.
Na $^{+}$ = 10 electrons = 2, 8
Mg $^{2 +}$ = 10 electrons = 2,8
O $^{2 -}$ = 10 electrons = 2,8
Si $^{2 +}$ = 12 electrons = 2,8,2
$⟹$ Si $^{2 +}$ is not isoelectronic with the rest.

Ka ìwé ẹ̀kọ́ nípa Acids, Bases And Salts (Nigeria Only) (WAEC)

Ka ìwé ẹ̀kọ́ nípa Atomic Structure And Bonding (JAMB)

Acids, Bases And Salts (Nigeria Only)

Atomic Structure And Bonding

Ibeere 33 Ìròyìn

The velocity, V of a gas is related to its mass, M by (k = proportionality constant)

V =

\frac{k}{M}

V =

\frac{k}{M^{\frac{1}{2}}}

V =

k M^{2}

V =

(\frac{k}{M})^{\frac{1}{2}}

Awọn alaye Idahun

Recall:
V = $\sqrt{\frac{3 R T}{M}}$
$∴ V \propto \frac{1}{\sqrt{M}}$
$V = \frac{k}{\sqrt{M}}$
V = $\frac{k}{M^{\frac{1}{2}}}$

Ka ìwé ẹ̀kọ́ nípa Kinetic Theory Of Matter And Gas Laws (JAMB)

Kinetic Theory Of Matter And Gas Laws

Ibeere 37 Ìròyìn

\( \mathrm{SO_3} \) is not directly dissolved in water in the industrial preparation of \( \mathrm{H_2SO_4} \) by the contact process because

SO

_{3}

is an acidic gas

Acid is usually added to water and not water to acid

The reaction between SO

_{3}

and water is violently exothermic

SO

_{3}

does not dissolve readily in water

Acids, Bases And Salts

Ibeere 39 Ìròyìn

Which of the following describes the chemical property of acids?

None of the above

Acid + XCO

_{3}

\to

Salt + H

_{2}

O + NH

_{3}

Acid + NaOH

\to

Normal salt + CO

_{2}

Acid + X

_{n}

CO

_{3}

\to

Salt + H

_{2}

O + CO

_{2}

Acids, Bases And Salts

Ibeere 40 Ìròyìn

Which of the following is a set of neutral oxides?

N

_{2}

O, H

_{2}

O, CO

N

_{2}

O, SO

_{2}

, CO

N

_{2}

O, Na

_{2}

O, ZnO

N

_{2}

O, SO

_{3}

, NO

Oxidation And Reduction

Tẹ́lẹ̀

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40