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 furring of kettles is caused by the presence of what compound in water?
calcium tetraoxosulphate (IV)
calcium hydrogentrioxocarbonate (IV)
calcium hydroxide
calcium trioxocarbonate (IV)
Correct answer is D
Calcium hydrogen carbonate, often present in temporary hard water, is boiled in a kettle to remove the hardness. In the process, a scale forms on the inside of the kettle in a process known as furring of kettles. This scale is composed of calcium carbonate.
Detergents are manufactured with straight hydrocarbon chains, is to make them
soluble
biodegradable
cheaper
foamy
Correct answer is B
Biodegradable because the straight hydrocarbons are natural and slightly soluble in water. Options A,C,D do not have strength hydrocarbon chains and they could harm the environment if they are made with the detergent
NH3(g) + HCl(s) → NH 4Cl (s)
The entropy change in the system above is
positive
zero
negative
intermediate
Correct answer is C
Entropy s is a measure of the degree of disorder or randomness of a substance. The entropy charge in the system is negative. Options B, C, D will not give negative but the result into positive
When sugar is dissolve in tea, the reaction is accomplished by?
positive change
negative entropy change
no entropy change
a minimum entropy change
Correct answer is C
There is no disorderliness so no entropy change.
The elements that belong to the third period of periodic table are
Li, Be, Al and D
Na, P, O and Cl
B, C, N, and O
Na, Mg, S and Ar
Correct answer is D
Na, Mg, S and Ar is the set of elements that belong to third period of the periodic table. Option A,B,C have elements which belong to the other period in the periodic table included in them.