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.
If the molecular mass of tetraoxosulphate (VI) acid is 98, calculate its vapour density.
196
49
106
82
Correct answer is B
Molecular mass = Vapour Density x 2
Vapour Density = \(\frac{\text{Molecular Mass}}{2}\)
Where Molecular mass = 98g/mol
Vapour Density = \(\frac{98}{2}\)
Vapour Density = 49g/mol
Which of these alloys contains copper?
solder
steel
permallory
bronze
Correct answer is D
Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon.
Calculate the percentage composition of oxygen in calcium trioxocarbonate(IV) [Ca=40, C=12, O=16]
16
48
40
12
Correct answer is B
Calcium trioxocarbonate (IV) = CaCO\(_3\)
Percentage of Oxygen = \(\frac{\text{Molar mass of 3O}}{\text{Molar mass of} CaCO_3}\) × 100%
Percentage of Oxygen = \(\frac{(3 \times 16)}{(40 + 12 + 48)}\) x 100%
Percentage of Oxygen = \(\frac{48}{100}\) x 100%
Percentage of Oxygen = 48%
The ionic radii of metals are usually
greater than their atomic radii
unaffected by the charge on the ion
the same as their atomic radii
less than their atomic radii
Correct answer is D
In a neutral atom, the atomic and ionic radius is the same, but many elements exist as anions or cations. If the atom loses its outermost electron (positively charged or cation), the ionic radius is smaller than the atomic radius because the atom loses an electron energy shell.
Yes ionic radius is only less than atomic radius for a metal.
In electrovalency, the oxidation number of the participating metal is always
decreasing
increasing
constant
neutral
Correct answer is B
In electro-valency the oxidation number of the participating metal increases.