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Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
The number of orbitals in a p-sub level of an atom is
A
2
B
3
C
5
D
6
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The p- orbital has 3 subshells; P\(_x\), P\(_y\) and P\(_z\) subshells.
Source: Myschool Past Questions Archive (Record #37731)
Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
Which of the following ions has an electron configuration different from the other?
A
17CI-
B
8O2-
C
12Mg2+
D
13AI3+
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
\(_{17}\)Cl\(^-\) = 18 electrons = 2, 8, 8
\(_{12}\)Mg\(^{2+}\), \(_{8}\)O\(^{2-}\) and \(_{13}\)Al\(^{3+}\) all have 10 electrons = 2, 8.
Source: Myschool Past Questions Archive (Record #37733)
Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
The atomic radii of metals are usually
A
greater than their ionic radii
B
equal to their ionic radii
C
less than their ionic radii
D
less than those of non-metals in the same period
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Metals give off electrons. This means that atomic radius is always greater than the ionic radius for metals.
Source: Myschool Past Questions Archive (Record #37734)
Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
Two elements, X and Y are in the same group on the periodic table because they both have the same
A
number of electronic shells
B
number of valence electrons
C
atomic size
D
atomic number
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The members of the same group always have the same number of electrons in the outer shell (i.e number of valence electrons).
Source: Myschool Past Questions Archive (Record #37735)
Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
The d-block elements are paramagnetic because they
A
contain paired electrons which are repelled by magnetic field
B
contain unpaired electrons in the partially filled 3d-orbital
C
contain paired electrons which are repelled by magnetic field force
D
have delocalized valence electrons
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Paramagnetism is a characteristic possessed by an atom with an unpaired electron.
Source: Myschool Past Questions Archive (Record #37739)
Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
Which of the following statements about a radioactive substance is/are correct? l. lt emits radiation continuously and spontaneously. ll. The emitted radiations are affected by temperature and pressure III. The radiation can penetrate opaque matter
A
ll only
B
l and ll only
C
l and lll only
D
ll and lll only
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The properties of radioactive elements holds true except that radioactive decay is not dependent on external conditions except electron capture and bombarding the radioactive material with subatomic particles.
Source: Myschool Past Questions Archive (Record #37742)
Chemistry
WAEC / WASSCE 2012
Matter & Separation Techniques
Solution
Which of the following elements is a metalloid?
A
Carbon
B
Oxygen
C
Silicon
D
Sodium
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Some examples of metalloids include boron, silicon, germanium, arsenic etc.
Source: Myschool Past Questions Archive (Record #37744)
Chemistry
WAEC / WASSCE 2012
Matter & Separation Techniques
Solution
Which of the following halogens is liquid at room temperature?
A
Chlorine
B
Fluorine
C
lodine
D
Bromine
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Bromine is the third lightest halogen. It is a fuming red-brown liquid at room temperature.
Source: Myschool Past Questions Archive (Record #37749)
Chemistry
WAEC / WASSCE 2012
Acids, Bases, and Salts
Solution
The shape of a graphite crystal is
A
tetrahedral
B
pyramidal
C
hexagonal
D
octahedral
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Graphite is a crystalline form of the element Carbon. The atoms are arranged in a hexagonal structure.
Source: Myschool Past Questions Archive (Record #37750)
Chemistry
WAEC / WASSCE 2012
Stoichiometry & Mole Concept
Solution
The number of sulphur atoms in 3.20g of SO\(_{2(g)}\) is [O = 16.0;S = 32.0; Avogadro constant = 6.02 x 10\(^{23}\)]
A
3.01 x 1022
B
6.02 x 1022
C
6.02 x1023
D
1.20 x 1024
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
32g of sulphur = 64g / 6.02 x 10\(^{23}\) atoms of SO\(_2\)
xg of sulphur = 3.2g of SO\(_2\)
: 1.6g of sulphur is present in 3.2g / 3.01 x 10\(^{23}\) atoms of SO\(_2\)
Source: Myschool Past Questions Archive (Record #37756)
Chemistry
WAEC / WASSCE 2012
Matter & Separation Techniques
Solution
Consider the reaction represented by the following equation: xCH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + zH\(_2\)O. The values of x,y and z respectively, are
A
2,3 and 4
B
2, 4 and 3
C
1,2 and 3
D
1, 3 and 5
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
xCH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + zH\(_2\)O
Balancing the equation, we have
C = x (on the left) and 2 (on the right)
⇒ x = 2
2CH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + zH\(_2\)O
On the left, H = 8 and on the right = 2z
⇒ 2z = 8 ; z = 4
2CH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + 4H\(_2\)O
On the right, O = 4 + 4 = 8.
On the left, O = 2 + 2y
⇒ 2 + 2y = 8
2y = 6 ; y = 3
x, y, z = 2, 3, 4.
Source: Myschool Past Questions Archive (Record #37757)
Chemistry
WAEC / WASSCE 2012
Matter & Separation Techniques
The formula of mercury (l) dioxonitrate (III) is
A
HgNO3
B
Hg2NO2
C
Hg2(NO2)2
D
Hg(NO3)2
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 #37762)
Chemistry
WAEC / WASSCE 2012
Matter & Separation Techniques
Solution
A sample of a gas may be identified as chlorine if it turns
A
damp blue litmus paper red
B
lime water miky
C
lead ethanoate paper black
D
starch iodide paper blue-black
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
A test for chlorine is to place damp starch-iodide paper into a test tube of chlorine. A positive result for chlorine is indicated by the paper turning from white to blue-black.
Source: Myschool Past Questions Archive (Record #37763)
Chemistry
WAEC / WASSCE 2012
Matter & Separation Techniques
Solution
A metal M forms two types of chlorine, MCl\(_2\) and MCl\(_3\) which of the following laws best explains the relationship between the chlorides? Law of
A
conservation of mass
B
definite proportion
C
multiple proportion
D
reciprocal proportion
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Law of multiple proportions, statement that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.
Source: Myschool Past Questions Archive (Record #37764)
Chemistry
WAEC / WASSCE 2012
Atomic Structure and Periodic Table
Solution
The complex compound formed by the combination of two elements with a large electronegativity difference is likely to be
A
polar covalent
B
giant molecular
C
covalent
D
ionic
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Ionic bonds are also formed when there is a large electronegativity difference between two atoms.
Source: Myschool Past Questions Archive (Record #37751)