set 3 MCQ Questions & Answers Detailed Explanation

Question : 1

The number of electrons in an element with atomic number X and atomic mass Y will be

a) (Y – X)

b) (X + Y)

c) (X – Y)

d) X

Question : 2

An oxide of nitrogen has molecular weight 30. What is the number of electrons in one molecule of the compound?

a) 22

b) 15

c) 14

d) 23

Question : 3

In a chemical change the total weight of the reacting substances compared to total weight of products is

a) always less

b) always more

c) never the same

d) always the same

Question : 4

Which of the following isotopes is used as the standard for atomic mass ?

a) ¹⁶O

b) ¹³C

c) ¹²C

d) ¹H

Question : 5

Which one of the following is not needed in a nuclear fission reactor?

a) Accelerator

b) Coolant

c) Moderator

d) Control device

Question : 6

Which of the following describes an isotope with a mass number of 99 that contains 56 neutrons in its nucleus ?

a) $↖43↙56{Ba}$

b) $↖99↙43{Tc}$

c) $↖99↙56{Ba}$

d) $↖56↙43{Tc}$