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.
The oxidation state of chlorine in NaClO3 is?
+1
+3
+5
+6
Correct answer is C
The oxidation number of chlorine in NaClO3 is +5.
When an ionic bond is broken, bonding electrons are
shared between participating atoms
gained by the most electropositive atom
gained by the most electronegative atom
lost by both participating atoms.
Correct answer is B
No explanation has been provided for this answer.
Group VIl elements in their combined states are called?
Halogens
Anions
Halide
Cations
Correct answer is C
Halide: A binary compound of a halogen with another element or group.
The most suitable process of obtaining water from an aqueous solution of sugar i
Crystallization
Distillation
Filtration
Decantation
Correct answer is B
- Crystallization is primarily employed as a separation technique to obtain pure crystals of a substance from an impure mixture.
- Another important application of crystallization is its use to obtain pure salt from seawater.
- Simple syrup crystallizes when enough of the sugar molecules stick to one another that they become insoluble in the water
note; distillation is used to obtain a solvent from a solution.
Which of the following pairs of properties of alkali metals decreases down the group?
First ionization energy and reactivity
melting point and atomic radius
Reactivity and electronegativity
First ionization energy and melting point
Correct answer is D
- The ionization energy of an atom is the amount of energy that is required to remove an electron from a mole of atoms in the gas phase:
- It is possible to remove more electrons from most elements, so this quantity is more precisely known as the first ionization energy, the energy to go from neutral atoms to cations with a 1+ charge.
- The ionization energy decreases from top to bottom in groups, and increases from left to right across a period.
- The boiling and melting points decrease as you move down the group.