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Chemistry
NECO SSCE 2008
Shapes of Molecules and Solids
Solution
The high boiling point of hydrogen fluoride can be explained in terms of?
A
covalent bonds.
B
dative bonds.
C
dipole-dipole bonds
D
electrovalent (ionic) bonds.
E
hydrogen bonds.
medium Difficulty
Verified Correct Answer: Option E
Chemical Principles & Mechanism
Hydrogen fluoride is formed through covalent bonding (electron sharing) between a hydrogen atom and a fluorine atom.
The reason is the strong electronegativity of the fluorine atom, which causes hydrogen and fluorine atoms to form hydrogen bonds in the liquid phase.
Source: WAEC / JAMB / NECO Classroom Archive (Record #43548)
Chemistry
WAEC / WASSCE 2008
Carbon Carbon Compounds
Solution
Diamond does not conduct electricity because it?
A
has no free valence electrons
B
is a giant molecule
C
contains no bonded electrons
D
is a solid at room temperature
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
It does not conduct electricity. Every atom in a diamond is bonded to its neighbours by four strong covalent bonds, leaving no free electrons and no ions .
Source: WAEC / JAMB / NECO Classroom Archive (Record #37284)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
Chlorophyll obtained from green leaves of plant can be shown to be composed of more than one coloured component by the technique of
A
crystallization
B
hydrolysis
C
chromatography
D
sublimation
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The chlorophyll from the green leaves of plant being a mixture can be separated by Chromatography into its different components. Chromatography has to do with the separation of coloured components. chromatography is used in industrial processes to purify materials, test trace amounts of contaminants, isolate chiral compounds, and quality control test products
Source: Myschool Past Questions Archive (Record #4006)
Chemistry
UTME / JAMB 2008
Acids, Bases, and Salts
Solution
In countries where the temperature falls below 273K, salt is always sprinkled on the icy road in order to
A
lower the melting point of the ice
B
increase the density of the ice
C
make the ice impure
D
raise the melting point of the ice
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The presence of impurities in a substance lowers the melting point. Salt is added on icy roads to cause the ice to melt on time.
Source: Myschool Past Questions Archive (Record #4007)
Chemistry
UTME / JAMB 2008
Stoichiometry & Mole Concept
Solution
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
From the equation above, calculate the mass of sodium hydroxide produced by 2.3g of sodium.
[H = 1, O = 16, Na = 23]
A
0.40g
B
0.80g
C
4.00g
D
8.00g
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Relative molecular mass of NaOH = 23 + 16 + 1 = 40smol-1
2 * 23g of sodium react with water to produce
2 * 40g of NaOH
∴ 2.3g of sodium will react with water to produce
(2.3 * 40 * 2)/(23 * 2) = 4.00g
Source: Myschool Past Questions Archive (Record #4011)
Chemistry
UTME / JAMB 2008
Stoichiometry & Mole Concept
Solution
16.8 g of sodium hydrogen trioxocarbonate (IV) is completely decomposed by heat. Calculate the volume of carbon(IV) oxide given off at s.t.p
[Na 23, C = 12, O = 16, H = 1, Molar volume of a gas at s.t.p = 22.4 dm3]
A
22.40 dm3
B
11.20 dm3
C
2.24 dm3
D
1.12 dm3
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2
Relative molecular mass of NaHCO3 = 23 +1 + 12 + 16 * 3 = 84gmol-1
2 * 84g of NaHCO3 will be liberated 22.4dm3 or CO2 at s.t.p
16.8g of NaHCO3 will liberate (16.8 * 22.4)/(2 * 84) = 2.24 dm3
Source: Myschool Past Questions Archive (Record #4019)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
300 cm3 of gas has a pressure of 800 mmHg. If the pressure is reduced to 650 mmHg, find its volume
A
243.75 cm3
B
369.23 cm3
C
738.46 cm3
D
1733.36 cm3
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
P1V1= P2V2
800 * 300 = 650 * V2
V2 = (800 * 300)/650 = 369.23 cm3
Source: Myschool Past Questions Archive (Record #4020)
Chemistry
UTME / JAMB 2008
Stoichiometry & Mole Concept
Solution
Diffusion is slowest in solid particles than in particles of liquid and gases because
A
solid particles have more kinetic energy than the particles of liquid and gases
B
solid particles have less kinetic energy than the particles of liqiud and gases
C
solid particles have less restriction in their movement than liquid and gas particles
D
the particles in solids are far apart and the cohesive forces between them are negligible
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Diffusion is faster in gases owing to their higher kinetic energy i.e increase in kinetic energy of molecules leads to increase in rate of diffusion.
Source: Myschool Past Questions Archive (Record #4021)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
The experiment that showed that atoms have tiny positively charged nucleus was first carried out by
A
Moseley
B
Rutherford
C
Millikan
D
Dalton
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The experiment that showed that atoms have tiny positively charged nuclei was first carried out by Rutherford. Rutherford's gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively charged nucleus.
Source: Myschool Past Questions Archive (Record #4022)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
The atom of an element X is represented as \(_z^yX\). The basic chemical properties of X depends on the value of
A
Y
B
Z
C
Y - Z
D
Z - Y
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The chemical properties of elements depend on their atomic numbers. The atomic number is represented by Z.
Source: Myschool Past Questions Archive (Record #4023)
Chemistry
UTME / JAMB 2008
Atomic Structure and Periodic Table
Diagram
Solution
The diagram above represent the electron sub-level for
Attached Figure / Diagram
A
carbon
B
nitrogen
C
oxygen
D
flourine
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The number of arrows indicates the number of electrons. Since the atomic number of oxygen is 8, the element is oxygen.
Source: Myschool Past Questions Archive (Record #4024)
Chemistry
UTME / JAMB 2008
Atomic Structure and Periodic Table
Solution
In the periodic table, the electrical and thermal conductivities are properties of elements that
A
decrease across the period and increase down the group
B
increase across the period and decrease down the group
C
decrease across the period and down the group`
D
increase acrosss the period and down the group
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
In the periodic table, electrical and thermal conductivities of elements decrease across the period and increase down the group.
Source: Myschool Past Questions Archive (Record #4025)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
\( _{11} ^{23}Na + _0^1n → _{11}^{24}Na \)
The reaction above is an example of
A
nuclear fission
B
nuclear fusion
C
artificial transmutation
D
beta decay
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Artificial transmutation. It is an artificially induced nuclear reaction caused by the bombardment of a nucleus with subatomic particles or small nuclei. It is also called artififcial radioactivity.
Source: Myschool Past Questions Archive (Record #4028)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
Air boiled out of water as steam is richer in
A
nitrogen and oxygen
B
carbon (IV) oxide and oxygen
C
noble gases and carbon (IV) oxide
D
oxygen and noble gases
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Air boiled out of water as steam is richer in carbon(IV)oxide and oxygen.
Source: Myschool Past Questions Archive (Record #4029)
Chemistry
UTME / JAMB 2008
Matter & Separation Techniques
Solution
When a few drops of water is added to a blue anhydrous cobalt (II) chloride, the colour changes to
A
white
B
pink
C
red
D
blue
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Blue anhydrous cobalt (II) chloride changes to pink in water.
Source: Myschool Past Questions Archive (Record #4032)