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Chemistry
UTME / JAMB 1998
Water, Solutions & Solubility
Solution
90.0g of MgCI2 was placed in 50.0cm3 of water to give a saturated solubility of the salt is 8.0 mol dm3 at the same temperature, what is the mass of the salt left undissolved at the given temperature?
(Mg = 24, Cl = 35.5)
A
52.0g
B
58.5g
C
85.5g
D
88.5g
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Molar mass of MgCl2 = 95g
The solubility of MgCl2 is 8.0/dm3
1 dm3 = 1000cm3
Solubility of g/cm3
8 x 95 → 1000cm3
x → 50
x = (50)/(1000) x (8 x 95) / (1) = 38g
Mass of the salt left undissolved = 90 - 38 = 52.0g
Source: Myschool Past Questions Archive (Record #13894)
Chemistry
UTME / JAMB 1998
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
Soap lather is an example of a colloid in which a?
A
liquid is dispersed in gas
B
solid is dispersed in liquid
C
gas is dispersed in liquid
D
liquid is despersed in liquid
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
When soap forms lather, a gas (primarily air) is dispersed within the liquid (soap and water mixture). This creates a frothy, bubbly substance, a foam. The gas is trapped within the bubbles formed by the soap molecules binding to water.
Source: Myschool Past Questions Archive (Record #13905)
Chemistry
UTME / JAMB 1998
Acids, Bases, pH & Salts
Solution
The pH of a solution obtained by mixing 100cm\(^3\) of a 0.1M HCl solution with 100cm\(^3\) of a 0.2M solution of NaOH is?
A
1.3
B
7.0
C
9.7
D
12.7
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Calculate Moles of Reactants:
Moles of HCl = Molarity x Volume in dm\(^3\) = 0.1 M x 0.1 dm\(^3\) = 0.01 moles
Moles of NaOH = Molarity x Volume in dm\(^3\) = 0.2 M x 0.1dm\(^3\) = 0.02 moles
Determine the Excess Reagent:
The neutralization reaction is a 1:1 ratio: HCl + NaOH → NaCl + H\(_2\)O
Excess NaOH = 0.02 - 0.01 = 0.01 mole
Calculate the Hydroxide Ion Concentration[OH\(^-\)]
Total Volume of the mixture = 100 cm\(^3\) + 100cm\(^3\) = 200 cm\(^3\) = 0.2dm\(^3\)
[OH\(^-\)] = \(\frac{0.01}{0.2}\) = 0.05M
Calculate pOH and pH
pOH = - Log[OH\(^-\)] = - Log[0.05]
= 1.3
But pOH + pH = 14
1.3 + pH = 14
pH = 14 - 1.3
= 12.7
Source: Myschool Past Questions Archive (Record #13907)
Chemistry
UTME / JAMB 1998
Oxidation, Reduction & Redox Reactions
Mg2+(aq) + 2e->(aq) → Mg(s)E°(volts) = 2.370
Zn2+(aq) + 2e->(aq) → Zn(s)E°(volts) = -0.763
Cds2+(aq) + 2e->(aq) → Cd(s)E°(volts) = 0.403
Cu2+(aq) + 2e->(aq) → Cu(s)E°(volts) = 0.340
In the electrochemical series above, the strongest reducing agents is?
A
Cu (s)
B
Cd(s)
C
Znsub>(s)
D
Mg(s)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #13908)
Chemistry
UTME / JAMB 1998
Stoichiometry, Mole Concept & Volumetric Analysis
2Cl2(g) + 2H2O(g) 4HCl(g) + O2(g)
∆H° = +115KJ mol-1. In the above equilibrium reaction, a decrease in temperature will?
A
favour the reverse reaction
B
favour the forward reaction
C
have no effect on the equilibrium state
D
double the rate of the reverse raection
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #13910)
Chemistry
UTME / JAMB 1998
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
2X(g) + Y(g) → Z(g): In the equation above, The rate of formation of Z is found to be independent of the concentration of Y and to quadruple when the concentration of X is doubled. The correct equation for the reaction is?
A
R = k (X)(Y)
B
R = K (X) ° (Y)
C
R = K (X) ° (Y) 2
D
R = K (X) 2(Y)°
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The problem states that the rate of formation of Z is independent of the concentration of Y. In chemical kinetics, if the rate does not change when the concentration of a reactant changes, the reaction is zero-order with respect to that reactant.
Order with respect to Y = 0. Mathematically, R ∝ [Y]\(^0\)
The problem also states that the rate quadruples (increases by a factor of 4) when the concentration of X is doubled. We can use the general rate proportion
Rate ∝ [Y]\(^n\)
When concentration is 2 [X], the rate is 4 R\(_1\),
This confirms the reaction is second-order with respect to X.
By combining the orders for both reactants, we get the overall rate equation: R = K [X]\(^2\)[Y]\(^0\)
Source: Myschool Past Questions Archive (Record #13911)
Chemistry
UTME / JAMB 1998
Non-Metals & Their Compounds
A gas that turns a filter paper previously soaked in lead ethanoate solution black is?
A
hyrogen chloride
B
hydrogen sulphide
C
sulphur (IV) oxide
D
sulphur (VI) oxide
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #13914)
Chemistry
UTME / JAMB 1998
Oxidation, Reduction & Redox Reactions
3CuO(s) + 2NH3(g) → 3Cu(s) + 3H2O(I) N2(g) (i).
2NH3(g) + 3Cl2(g) → 6HCl(g) + N2(g) (ii).
4NH3(g) + 3O2(g) → 6H2O(I) + 2N2(g) (iii).
The reactions represented by the equations above demonstrate the?
A
basic properties of ammonia
B
acidic properties of ammonia
C
reducing properties of ammonia
D
oxidizing properties of ammonia
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #13915)
Chemistry
UTME / JAMB 1998
Stoichiometry, Mole Concept & Volumetric Analysis
A solution containing chloride ions gives white precipitate with silver trioxonitrate(V) Solution. The precipitate will be insoluble in dilute?
A
HNO 3 but soluble in ammonia solution
B
HNO3 and ammonia solution
C
HCl but soluble in ammonia solution
D
HCl and in ammonia solution
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #13920)
Chemistry
UTME / JAMB 1998
Metals, Transition Elements & Extraction
Solution
Which of the following is observed when a solution of iron (III) chloride is mixed with a solution of sodium hydroxide?
A
A gas is evolved
B
A deep blue precipitate is formed
C
The resultant solution turns green turns
D
A brown precipitate is formed
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
iron(III) chloride is a yellow solution
sodium hydroxide is colourless
iron(III) hydroxide is a reddish brown precipitate
sodium chloride is colourless
So in the reaction, yellow solution when added to sodium hydroxide forms reddish brown precipitate that is insoluble in excess sodium hydroxide.
Source: Myschool Past Questions Archive (Record #13923)
Chemistry
UTME / JAMB 1998
Stoichiometry, Mole Concept & Volumetric Analysis
The metal that will react with water only in the form of steam to librate hydrogen gas is?
A
calcium
B
aluminium
C
iron
D
zinc
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #13925)
Chemistry
UTME / JAMB 1998
Oxidation, Reduction & Redox Reactions
A common characteristic shared by iron and aluminium is that both?
A
are extracted by reduction methods
B
form only basic oxides
C
show oxidation states of +2 and +3
D
form soluble hydroxides
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #13926)
Chemistry
UTME / JAMB 1998
Metals, Transition Elements & Extraction
Alloys are often used in preference to pure metals because?
A
metals are too hard
B
merals are ductile
C
metallic properties are improve in alloys
D
alloys are a mixture of metals
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #13927)
Chemistry
UTME / JAMB 1998
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
One mole of hydrocarbon contains 6g of hydrogen. If the molecular weight is 54, the hydrocarbon is an?
A
alkanone
B
alkane
C
alkene
D
alkyne
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
CxH6
∴ CxH6 = 54
12x + 6 = 54
12x = 54 - 6
12x = 48
x = (48)/(12)
x = 4
We have CxH6 butyne
A formular of alkyne
Source: Myschool Past Questions Archive (Record #13929)
Chemistry
UTME / JAMB 1998
Organic Chemistry I: Hydrocarbons & Crude Oil
On cracking medicinal paraffin, a gas is evolved which gives a pop sound with a lighted splinter and an oily liquid which decolourizes bromine solution is also obtained. The products of the cracking are ?
A
carbon (IV) oxide and alkyne
B
carbon (ll) oxide and alkene
C
hydrogen gas and alkene
D
hydrogen gas and alkane
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #13933)