Chemistry Past Questions and Answers

The temperature of a body decreases when drops of liquid placed on it evaporate because?

A The atmospheric vapour pressure has a cooling effect on the body
B A temperature gradient exists between the drops of liquid and the body causing the latter to vaporate
C The heat of vapourization is drawn from the body causing it to cool
D The random motion of the liquid molecules causes a cooling effect on the body

Question 7:

The electron configuration of two elements with similar chemical properties are represented by?

A 1s²2s²2p⁵ and 1s²2s²2p⁴
B 1s²2s²2p⁴ and 1s²2s²2p⁶3s¹
C 1s²2s²2p⁶3s¹ and 1s²2s¹
D 1s²2s²2p⁴ and 1s²2s¹

Question 8:

In the periodic table, what is the property that decreases along the periodic and increases down the group?

A Atomic number
B Electron affinity
C Ionization potential
D Atomic radius

Question 9:

Two elements, P and Q with atomic numbers 11 and 8 respectively , combine chemically to form the compound P_xQ_Y. The respective values of x and y are?

A 1 and 1
B 1 and 2
C 2 and 1
D 3 and 1

Question 10:

Oxygen is a mixture of two isotopes 16-O and 18-O with relative abundances of 90% and 10% respectively. The relative atomic mass of oxygen is?

A 16.0
B 16.2
C 17.0
D 18.0