JAMB Past Questions and Answers - Page 1369

6,841.

When element \(_{20}\)Y combines with element \(_8\)Z, it forms

A.

A covalent compound , YZ is formed

B.

A covalent compound, ZY is formed

C.

An ionic compound, YZ is formed

D.

An ionic compound, ZY is formed

Correct answer is C

Y = 2,8,8,2 and Z = 2,6.

Y will readily give off its 2 valence electrons and Z will accept the 2 electrons in order to achieve octet configuration. Hence, the compound YZ is formed by ionic bonding.

6,842.

How many electrons are present in \(^9_4Be^{2+}\)?

A.

2

B.

4

C.

5

D.

6

Correct answer is A

Neutral Be has 4 electrons but \(Be^{2+}\) means it has lost two electrons from possible four and became a positive ion. 

\(\therefore\) the number of electrons left will be equal to two.

6,843.

An atom X consist of 6 protons, 6 electrons and 7 neutrons. Which of the following representations of the atom is correct?

A.

136X

B.

137X

C.

196X

D.

197X

Correct answer is A

No explanation has been provided for this answer.

6,844.

The following atoms of carbon 126C, 136C and 146C can be described as?

A.

Allotropes

B.

Isomers

C.

Isotopes

D.

Isotones

Correct answer is C

No explanation has been provided for this answer.

6,845.

N2O4(aq) \(\rightleftharpoons\) 2NO2(g) \(\bigtriangleup\)H = +ve

In the reaction above, an increase in temperature will

A.

Increase the reactant production

B.

Increase the value of the equilibrium constant

C.

Shift the equilibrium to the left

D.

Decrease the value of the equilibrium constant

Correct answer is B

No explanation has been provided for this answer.