Chemistry questions and answers

Chemistry Questions and Answers

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.

746.

The oxidation number of iodine in KIO3 is

A.

+7

B.

+3

C.

+5

D.

+6

Correct answer is C

If the rules are followed, it is non-negotiable that +5 is the suitable answer to the question.

747.

A given mass of gas occupies 2dm3 at 300k. At what temperature will its volume be doubled, keeping the pressure constant?

A.

400k

B.

480k

C.

550k

D.

600k

Correct answer is D

At constant pressure connotes Charle's law

\(\frac{V_1}{T_1}\) = \(\frac{V_2}{T_2}\)

\(\frac{2dm^3}{300k}\) = 2 x \(\frac{2dm^3}{T_2}\)

T2= 600k

748.

For a general equation of the nature xP + yQ → mR + nS, the expression for the equilibrium constant is

A.

k [P]x [Q]y

B.

\(\frac{[P]^x [Q]^y}{[R]^m [S]^n}\)

C.

\(\frac{[R]^m [S]^n}{[P]^x [Q]^y}\)

D.

\(\frac{m[R] n[S]}{x[P] y[Q] }\)

Correct answer is C

Expression for equilibrium constant

k = \(\frac{\text{concentration of product}}{\text{concentration of reactant}}\)

749.

The constituent of air necessary in the rusting process are

A.

O2 and H2O

B.

Ar and CO2

C.

CO2 and H2O

D.

O2 and CO2

Correct answer is A

Rust is an iron oxide, a usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture.

750.

In the laboratory preparation of ethyl ethanoate, the water present in the mixture is removed using ?

A.

Anhydrous CaCl2

B.

concentrated NaCO4

C.

dilute NaOH

D.

concentrated H2SO4

Correct answer is A

To purify the distillate of impurities like unreacted ethanol, acids, water and ethoxyethane.

Adding anhydrous calcium chloride and leave it to stand for a day to remove any water present

in the mixture.