JAMB Chemistry Past Questions & Answers - Page 276

1,376.

A particle that contains 8 proton, 9 neutrons and 7 electrons could be written as?

A.

O

B.

O+

C.

N

D.

O-

Correct answer is B

The atomic number is the number of protons in the nucleus of an atom.

The number of protons define the identity of an element (i.e., an element with 8 protons is a carbon atom, no matter how many neutrons may be present).

If an atom loses or gains electrons, it will become a positively or negatively charged particle, called an ion.

The loss of one or more electrons results in more protons than electrons and an overall positively charged ion, called a cation.

1,377.

A liquid begins to boil when?

A.

its vapour pressure is equal to the vapour pressure of its solid at the given temperature

B.

molecules start escaping from its surface

C.

its vapour pressure equals the atmosphere pressure

D.

its volume is sightly increased

Correct answer is C

The normal boiling point is the temperature at which the vapour pressure is equal to the standard sea-level atmospheric pressure.

1,380.

What volume of oxygen will remain after reacting 8cm3 of hydrogen with 20cm3 of oxygen?

A.

10 cm3

B.

12 cm3

C.

14 cm3

D.

16 cm3

Correct answer is D

No explanation has been provided for this answer.