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Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
The two ions responsible for hardness in water are
A
Ca\(^{2+}\) and / or Mg\(^{2+}\)
B
K\(^+\) and / or Mg\(^{2+}\)
C
Ca\(^{2+}\) and / or Li\(^+\)
D
Ca\(^{2+}\) and / or Na\(^+\)
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 #55822)
Chemistry
UTME / JAMB 2019
Organic Chemistry
Which of the following could not be alkane?
A
C\(_4\)H\(_{10}\)
B
C\(_5\)H\(_{12}\)
C
C\(_7\)H\(_{14}\)
D
C\(_8\)H\(_{18}\)
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 #55824)
Chemistry
UTME / JAMB 2019
Atomic Structure and Periodic Table
Solution
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.
A
Z\(_3\)(SO\(_4\))\(_2\)
B
ZSO\(_4\)
C
Z\(_2\) SO\(_4\)
D
Z\(_2\)(SO\(_4\))\(_3\)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Z = 1s\(^2\) 2s\(^2\) 2p\(^6\) 3s\(^2\) 3p\(^1\)
\(\therefore\) We have Z\(^{3+}\) and SO\(_4 ^{2-}\)
The reaction : Z\(^{3+}\) + SO\(_4 ^{2-}\) \(\to\) Z\(_2\)(SO\(_4\))\(_3\).
Source: Myschool Past Questions Archive (Record #55998)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
The hybridization in the compound \(CH_3 - CH_2 - C \equiv H\) is
A
sp\(^3\) and sp
B
sp
C
sp\(^2\)
D
sp\(^3\) and sp\(^2\)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The hybridization in a and b is sp\(^3\) hybridization while in c and d is sp hybridization.
Source: Myschool Past Questions Archive (Record #55999)
Chemistry
UTME / JAMB 2019
Atomic Structure and Periodic Table
Solution
The following are isoelectronic ions except
A
Na\(^+\)
B
Mg\(^{2+}\)
C
Si\(^{2+}\)
D
O\(^{2+}\)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
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
\(\implies\) Si\(^{2+}\) is not isoelectronic with the rest.
Source: Myschool Past Questions Archive (Record #56000)
Chemistry
UTME / JAMB 2019
Kinetics, Energetics and Equilibrium
Solution
Consider the reaction: A + 2B\(_{(g)} \rightleftharpoons \) 2C + D\(_{(g)}\) (\(\Delta\)H = +ve)
What will be the effect of decrease in temperature on the reaction?
A
Rate of backward reaction will increase
B
The equilibrium constant will shift
C
Rates of forward and backward reactions are not affected
D
Rate of forward reaction will increase
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The given reaction is endothermic, hence, a decrease in temperature will favor the exothermic side which is the backward reaction.
Source: Myschool Past Questions Archive (Record #56001)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
A cell shorthand notation can be written as A / A\(^+\) // B\(^{2+}\) /B. The double slash in the notation represents the
A
electrolyte
B
electrodes
C
salt bridge
D
solid - liquid interface
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 #56002)
Chemistry
UTME / JAMB 2019
Atomic Structure and Periodic Table
Solution
The shapes of water, ammonia, carbon (iv) oxide and methane are respectively
A
linear, tetrahedral, angular and pyramidal
B
angular, pyramidal, linear and tetrahedral
C
pyramidal, linear, tetrahedral and angular
D
tetrahedral, angular, pyramidal and linear
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Ammonia \((NH_3\)) has a trigonal pyramidal structure with a bond angle of approximately 107 degrees. Methane (\(CH_4\)) has a tetrahedral structure with a bond angle of 109.5 degrees. Carbon dioxide is a linear molecule, with a 180-degree bond angle. Water \((H_2O\)) has a bent or V-shaped structure with a bond angle of approximately 104.5 degrees.
Source: Myschool Past Questions Archive (Record #56003)
Chemistry
UTME / JAMB 2019
Atomic Structure and Periodic Table
Solution
Which quantum divides shells into orbitals?
A
Spin
B
Principal
C
Azimuthal
D
Magnetic
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The azimuthal quantum number determines an atom's orbital angular momentum and the shape of the orbital. The principal quantum number determines its number of shells. Magnetic quantum number determines how many orbitals there are as well as their orientation within a subshell.
Source: Myschool Past Questions Archive (Record #56004)
Chemistry
UTME / JAMB 2019
Electrochemistry and Redox
Solution
The oxidation state(s) of nitrogen in ammonium nitrite is/are
A
-3, +3
B
+5
C
-3, +5
D
-3
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Ammonium nitrite = NH\(_4\)NO\(_2\)
NH\(_4 ^+\): Let the oxidation number of Nitrogen = x
x + 4 = 1 \(\implies\) x = 1 - 4
x = -3
NO\(_2 ^-\): x - 4 = -1
x = -1 + 4 \(\implies\) x = +3.
The oxidation numbers for Nitrogen in Ammonium Nitrite = -3, +3.
Source: Myschool Past Questions Archive (Record #56005)
Chemistry
UTME / JAMB 2019
Atomic Structure and Periodic Table
Solution
Hydrogen bond is a sort of
A
van der waals force
B
dative bond
C
ionic bond
D
a covalent bond
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Hydrogen bonding is a type of Van der Waals force, specifically a strong dipole-dipole interaction. It's a distinct type of intermolecular attraction, not a covalent bond, though it's stronger than most other Van der Waals forces like London dispersion forces.
Source: Myschool Past Questions Archive (Record #56006)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
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
A
Ca(OH)\(_2\) and NaOH
B
Na\(_2\)CO\(_3\)
C
NaCl
D
NaOH
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Soda lime is a mixture of caustic soda (NaOH) and lime water (Ca(OH)\(_2\)).
Source: Myschool Past Questions Archive (Record #56007)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
Which of the following sets of operation will completely separate a mixture of sodium chloride, sand and iodine?
A
addition of water, filtration, evaporation to dryness and sublimation
B
filtration, evaporation to dryness, addition of water and sublimation
C
sublimation, filtration, evaporation and addition of water
D
sublimation, addition of water, filtration and evaporation to dryness
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Process:
Add water to the mixture and then filter. The resultant is a salt solution as your filtrate and a mixture of iodine and sand as your residue. Evaporate the filtrate to dryness to get your sodium chloride (salt). Heat the residue to sublime the iodine from the sand.
Addition of water \(\to\) Filtration \(\to\) Evaporation \(\to\) Sublimation.
Source: Myschool Past Questions Archive (Record #56008)
Chemistry
UTME / JAMB 2019
Stoichiometry & Mole Concept
Solution
200cm\(^3\) of 0.50mol/dm\(^3\) solution of calcium hydrogen trioxocarbonate (IV) is heated. The maximum weight of solid precipitated is
A
10g
B
25g
C
20g
D
15g
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Equation: Ca(HCO\(_3\))\(_2\) \(\to\) CaCO\(_3\) (precipitate) + H\(_2\)O + CO\(_2\) (in the presence of heat)
V = 200 cm\(^3\) = 0.2 dm\(^3\)
C = 0.5 mol/dm\(^3\) = 0.5M
N = CV \(\implies\) N = 0.5 \(\times\) 0.2
= 0.1 mole
From the equation 1 mole of Ca(HCO\(_3\))\(_2\) gives 100g of CaCO\(_3\)
(1 mole CaCO\(_3\) = 40 + 12 + (3 x 16) = 100g\)
0.1 mole of Ca(HCO\(_3\))\(_2\) gives x g of CaCO\(_3\).
\(\frac{1}{0.10} = \frac{100}{x}\)
\(x = 100 \times 0.10 = 10 g\)
Source: Myschool Past Questions Archive (Record #56009)
Chemistry
UTME / JAMB 2019
Kinetics, Energetics and Equilibrium
Solution
Which of the following conditions will most enhance the spontaneity of a reaction?
A
\(\Delta\)H is negative and greater than T\(\Delta\)S
B
\(\Delta\)H is negative and \(\Delta\)S = 0
C
\(\Delta\)H is positive and less than T\(\Delta\)S
D
\(\Delta\)H is positive and equal to T\(\Delta\)S
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
A reaction is spontaneous when the Gibbs free energy change (\DeltaG) is negative. This is determined by the equation \DeltaG = \DeltaH - T\DeltaS, where \DeltaH is the enthalpy change, T is the temperature, and \DeltaS is the entropy change. Therefore, a reaction is spontaneous if \DeltaH is negative and T\DeltaS is negative, or if \DeltaH is positive and T\DeltaS is positive and greater than \DeltaH. In other words, for a reaction to be spontaneous, the decrease in enthalpy (\DeltaH) must be greater than the increase in entropy (T\DeltaS).
In summary: For a reaction to be spontaneous, either \DeltaH must be negative (exothermic) and T\DeltaS must be smaller than \DeltaH, or T\DeltaS must be positive and larger than \DeltaH. The key is to ensure that the decrease in Gibbs free energy (\DeltaG < 0) is negative.
Applying values to those parameters, options A, B and C appear correct because they'll all make \DeltaG negative but the one that will mostly enhance spontaneity is option A because \DeltaG = -ve, \DeltaH = - ve.
Source: Myschool Past Questions Archive (Record #56010)