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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.

701.

Calculate the amount in moles of silver deposited when 9650C of electricty is passed through a solution of silver salt [= 96500 Cmol-1]

A.

0.05

B.

10.80

C.

10.00

D.

0.10

Correct answer is D

m = Mm×Q96500n

where Q = IT

M = Mm × Q96500n

where m = mass

Mm = Molar mass

Q = Quantity of electricity

n = number of change= +1

MMm = mole = massMolarmass

MMm = Q96500n

= 965096500n × 1

= 110 = 0.1mol

702.

Tin is unaffected by air at ordinary temperature due to its?

A.

Low melting point

B.

Weak electropositive character

C.

High boiling point

D.

White lustrous appearance

Correct answer is A

Tin has a melting point of 232° which enables it to be unaffected by air at ordinary temperature coupled with the fact that it also helps in making a good metal for alloying.

Tin is relatively unaffected by both water and oxygen at room temperature due to its low melting point. It does not rust, corrode, or react in any other way. This explains one of its major uses: as a coating to protect other metals.

703.

The mass of silver deposited when a current of 10A is passed through a solution of silver salt for 4830s is – (Ag = 108 F = 96500(mol-1)

A.

54.0g

B.

27.0g

C.

13.5g

D.

108.0gQ

Correct answer is A

Recall that

mass deposited = MmIt96500n

Mm =108, t = 4830s

I = 10A, n = 1

m = 108 × 10 × (483096500) × 1

m = 54.0g

704.

The shape of ammonia molecules is

A.

trigonal planar

B.

octahedral

C.

square planar

D.

tetrahedral

Correct answer is A

Ammonia = NH3

It has three bonds of hydrogen to the Nitrogen.

705.

22688Rax86Rn + alpha particle

A.

226

B.

220

C.

227

D.

222

Correct answer is D

22688Rax86Rn + 42He

42He = alpha particle

considering the summation of the mass number

226 = x + 4

x = 226 - 4

x = 222