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Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
56.00cm3 of a gas at S.T.P. weighed 0.11g. What is the vapour density of the gas?
[Molar volume of a gas at S.T.P = 22.4dm3]
A
11.00
B
22.00
C
33.00
D
44.00
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
56.00cm3 of a gas at S.T.P weighed 0.11g
Molar volume of the gas = 22.4dm3 = 22400cm3
molar mass = (22400 x 0.11)/56
molar mass = 2464/56 = 44
Vapour density = Molar mass/2 = 44/2 = 22
Source: Myschool Past Questions Archive (Record #828)
Chemistry
UTME / JAMB 1999
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Which of the following gases will diffuse fastest when passed through a porous plug?
[H = 1, C = 12, N = 14, O = 16]
A
Propane
B
Oxygen
C
Methane
D
Ammonia
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The rate of diffusion is inversely proportional to the square root of the relative molecular mass; in other words, lighter molecules diffuse faster than heavier ones.
The relationship between diffusion rate and molecular mass is an inverse one. This means that as the molecular mass of a substance increases, its diffusion rate decreases. Conversely, substances with lower molecular masses will diffuse more quickly.
Relative molecular mass of :
(a) Propane, C\(_3\)H\(_8\) = (12 x 3) + (1 x 8) = 36 + 8 = 44
(b) Oxygen, O\(_2\) = 16 x 2 = 32
(c) Methane, CH\(_4\) = 12 + (1x4) = 12 + 4 = 16
(d) Ammonia, NH\(_3\) = 14 + (1 x 3) = 17
Since CH\(_4\) has the least molecular mass compared to other options, it has the highest diffusion rate.
Source: Myschool Past Questions Archive (Record #829)
Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which is the temperature of a given mass of a gas initially at 0°C and 9 atm, if the pressure is reduced to 3 atm at constant volume?
A
91K
B
182K
C
273K
D
819K
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
From P1/T1 = P2/T2 = 9/273 = 3/T2
T2 x 9 = 273 x 3
T2 = (273 x 3)/9
T2 = 91K
Source: Myschool Past Questions Archive (Record #830)
Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following will have its mass increased when heated in air?
A
Helium
B
Magnesium
C
Copper pyrites
D
Glass
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 #831)
Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
From the equation above, the mass of magnesium required to react with 250cm3 of 0.5M HCl is
[Mg = 24]
A
0.3g
B
1.5g
C
2.4g
D
3.0g
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Molar conc. =no.of moles／Vol in dm3
Vol=250cm3= 0.25dm3
Molar conc=0.5M
No of moles=molar conc *Vol in dm3
=0.5*0.25
=0.125mole of HCl
2moles of HCl → １Mole of Mg
0.125 mole →(0.125*1)/2
=0.0625mole of Mg
Reacting mass=no of moles* molar mass
Mg=24
Mass=0.0625*24
=1.5g
Source: Myschool Past Questions Archive (Record #832)
Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
A gaseous metallic chloride MClx consists of 20.22% of M by mass. The formula of the chloride is?
[M = 27, Cl = 35.5]
A
MCl
B
MCl2
C
MCl3
D
M2Cl6
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Percentage by mass of M = 20.22%
Percentage by mass of Cl = x
100 - 20.22 = 79.78%
Mass given ratio of M
M = \(\frac{20.22}{27}\) = 0.75
Chlorine = \(\frac{79.78}{35.5}\) = 2.24
Divide by the smallest
M = \(\frac{0.75}{0.75}\) = 1
Cl = \(\frac{2.24}{0.75}\) = 3
∴ The formula = MCl\(_3\)
Source: Myschool Past Questions Archive (Record #836)
Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
In which of the following are water molecules in the most disorderly arrangement?
A
Ice at -10°C
B
Ice at 0°C
C
Water at 100°C
D
Steam at 100°C
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The gaseous state of matter has the most disorderly arrangement of particles. Hence, steam (water in gaseous form) is the most disorderly arrangement on the list.
Source: Myschool Past Questions Archive (Record #837)
Chemistry
UTME / JAMB 1999
Periodic Table & Periodicity
In order to remove one electron from a 3S orbital of gaseous sodium atom, about 496KJMol-1 of energy is required. This energy is referred to as
A
electron affinity
B
ionization energy
C
activation evergy
D
electronegativity
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 #838)
Chemistry
UTME / JAMB 1999
Acids, Bases, pH & Salts
Solution
Nitrogen obtained from the liquefaction of air has a higher density than that obtained from nitrogen containing compounds because the former contains
A
water vapour
B
oxygen
C
carbon (IV) oxide
D
rare gases
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The correct answer is rare gases because when nitrogen is obtained from air, \(CO_2\) and \(O_2\) are removed by passing air through caustic soda and heated copper turnings respectively.
However, the nitrogen obtained this way contains about 1% by volume of rare gases as impurities, these rare gases make it denser than nitrogen obtained from nitrogen compounds like ammonia, etc
Source: Myschool Past Questions Archive (Record #839)
Chemistry
UTME / JAMB 1999
Water, Solutions & Solubility
Solution
The method that can be used to convert hard water to soft water is
A
chlorination
B
passage over activated charcoal
C
the use of an ion-exchange resin
D
aeration
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Ion-exchange resins(small, porous beads that have a fixed negative charge) are commonly used to convert hard water to soft water by replacing calcium and magnesium ions (which cause hardness) with sodium or potassium ions.
When hard water passes through the resin beads, the calcium and magnesium ions are attracted to the negatively charged resin and displace the sodium or potassium ions that were originally attached. The water that flows out of the resin bed is now "softened" because it contains sodium or potassium ions instead of calcium and magnesium ions.
After a period of time, the resin beads become saturated with calcium and magnesium ions and need to be "regenerated". This is done by flushing the resin bed with a concentrated salt solution (sodium chloride), which displaces the calcium and magnesium ions and allows the resin to be recharged with sodium ions.
Source: Myschool Past Questions Archive (Record #840)
Chemistry
UTME / JAMB 1999
Atomic Structure, Orbitals & Nuclear Chemistry
1s2, 2s2, 2p6, 3s2, 3p6, 3d7, 4s2
An element with the electronic configuration above is a
A
non-metal
B
metal
C
transition element
D
group two element
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 #841)
Chemistry
UTME / JAMB 1999
Chemical Bonding & Intermolecular Forces
Solution
Given that electronegativity increases across a period and decreases down a group in the periodic table, in which of the following compounds will the molecules be held together by the strongest hydrogen bond?
A
HF(g)
B
NH3(g)
C
CH4(g)
D
HCl(g)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Among HF, NH\(_3\), CH\(_4\), and HCl, HF has the strongest hydrogen bond. The reason is because the strength of a hydrogen bond depends on the electronegativity of the atom bonded to hydrogen and the size of the atom. HF's combination of the most electronegative atom and a relatively small size makes it the strongest hydrogen bond among the given molecules. Fluorine (F) is the most electronegative element, creating a large dipole moment in HF, which results in a strong hydrogen bond.
Source: Myschool Past Questions Archive (Record #842)
Chemistry
UTME / JAMB 1999
Acids, Bases, pH & Salts
Solution
0.25 mole of hydrogen chloride was dissolved in distilled water and the volume made up of 0.50 dm3. If 15.0 cm3 of the solution requires 12.50 cm3 of aqueous sodium trioxocarbonate (IV) for neutralization, calculate the concentration of the alkaline solution
A
0.30 mol dm3
B
0.40 mol dm3
C
0.50 mol dm3
D
0.60 mol dm3
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
M1 V1 = M2 V2
∴ Mn Vn represent volume and molar concentration of HCL also MyVy represent volume and molar concentration of Na2CO3
MnVn = MyVy
0.25 * 15 = 12.50 * My
My = (0.25 * 15)/12.50
My = 0.3m/dm3
Source: Myschool Past Questions Archive (Record #1375)
Chemistry
UTME / JAMB 1999
Oxidation, Reduction & Redox Reactions
The correct order of increasing oxidation number of the transition metal ions for the compounds K2Cr2O7, V2O5 and KMnO4 is
A
V2O5 2Cr2O7 4
B
K2Cr2O7 4 2O5
C
KMnO4 2Cr2O7 2O5
D
KMnO4 2O5 2Cr2O7
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 #1378)
Chemistry
UTME / JAMB 1999
Stoichiometry, Mole Concept & Volumetric Analysis
The set of pollutants that is most likely to be produced when petrol is accidentally spilled on plastic materials and ignited is
A
CO, CO2 and SO2
B
CO, HCL and SO2
C
CO, CO2 and HCL
D
SO2, CO2 and HCL
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 #1379)