WAEC Chemistry Past Questions & Answers - Page 39

191.

The number of electrons in the 3d orbital of  \(_24\)Cr is

A.

2

B.

3

C.

4

D.

5

Correct answer is D

Its electronic configuration in ground state is 1s2 2s2 2p6 3s2 3p6 4s1 3d5.

192.

The atoms of \(^{64}_{29}\)Cu and \(^{65}_{30}\)Zn have the same number of?

A.

nucleon

B.

electrons

C.

neutrons

D.

protons

Correct answer is C

The atomic mass is written as superscript  = proton number + neutron number

- Atomic mass of Cu is 64 = 29 + 35

- Atomic mass of Zn is 65 = 30 + 35

Proton number is written as subscript

193.

One of the deductions from Rutherford's alpha particle scattering experiment is that?

A.

electrons are negatively charged

B.

electrons have a negligible mass

C.

nuclei of atoms are positively charged

D.

protons are positively charged

Correct answer is C

The model of an atom put forward by Ernest Rutherford in 1911 on the basis of experiments on the scattering of alpha particles. The model consisted of a very dense positively charged nucleus, with electrons orbiting round the nucleus. 

194.

Which of the following apparatus is NOT used in volumetric analysis?

A.

Pipette

B.

Burette

C.

Desiccator

D.

conical flask

Correct answer is C

- The most common apparatus used in volumetric determinations are the pipette,buret, measuring cylinder, volumetric and conical (titration) flask.

-  A common use for desiccators is to protect chemicals which are hygroscopic or which react with water from humidity.

195.

In Boyle's law?

A.

T is constant, P varies directly with V

B.

P is constant, V varies inversely with T

C.

V is constant, P varies directly with T

D.

T is constant, V varies inversely with P

Correct answer is D

Boyle's law states that the pressure (p) of a given quantity of gas varies inversely with its volume (v) at constant temperature; i.e., in equation form, pv = k, a constant. ...