Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.
Which of the following metals does not react with water to produce hydrogen?
Copper
Potassium
Sodium
Zinc
Correct answer is A
Most alkali metals and alkaline earth metals react with water to produce hydrogen. The alkali metals comprise Group 1 of the periodic table, and include lithium, sodium, potassium, etc.
- Zinc is not much reactive with cold or room temperature water but reacts with steam to form zinc oxide and liberate hydrogen gas.
- Copper lies below hydrogen in the activity series of metals, therefore it can not displace hydrogen from water
"Electrons always occupy the lowest empty energy level" is a statement of
Aufbau Principle
Hund's rule
Pauli Exclusion Principle
Periodic law
Correct answer is A
- The Aufbau principle states that electrons fill lower-energy atomic orbitals before filling higher-energy ones
0.010
0.020
0.100
0.150
Correct answer is B
\(frac{CaVa}{CbVb}\) = \(frac{Na}{Nb}\)
( 0.01 X 20 ) / (Cb X 20) = 1 / 2
cross multiply → Cb = (0.01 X 20 X 2) / ( 20 X 1)
Cb = 0.02 mol/dm\(^3\)
How many moles of H\(_2\)SO4 are there in 50 cm\(^3\) of 0.108 mol dm\(^3\) solution of the acid?
5.4x 10
5.4 x 10\(^{-3}\)
5.4 x 10\(^{-2}\)
5.4x 10\(^{-1}\)
Correct answer is B
No. of moles = \(\frac{molar conc \times volume}{1000}\)
No. of moles = \(\frac{0.108 \times 50}{1000}\)
: No. of moles = 0.0054 moles = \( 5.4 \times 10^{-3}\)
Which of the following statements about the solubility of a salt is correct?
A salt whose solubility increases with temperature would not crystallize easily on cooling
A salt whose solubility is independent of temperature would normally crystallize out on cooling
Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature
Solubility of a solid does not affect its crystallization
Correct answer is C
Crystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound.