Chemistry Past Questions and Answers

What is the partial pressure of hydrogen gas collected
over water at standard atmospheric pressure and 25 ^oC if the saturation vapour pressure of water at saturation vapour pressure of water is 23 mm Hg at that temperature?

A 737 mm Hg
B 763 mm Hg
C 777 mm Hg
D 783 mm Hg

Question 7:

The atomic radius of Li, Na and K are 1: 33A, 1. 54A and 1. 96A res pectively. Which of the following explaqins this gradation in atomic radius?

A Electropositivity decreases from Li to Na to K
B Electronegativity decreases from Li to Na to K
C The number of the electron shells increases from Li to Na to K
D The elements are in the same period

Question 8:

Elements X and Y have electronic configurations 1s²2s²2p⁶ and 1s²2s²2p⁶3s²3p¹ respectively. When they combine, the formula of the compound formed is

A XY
B YX
C X₂Y₃
D Y₂X₃

Question 9:

The atomic number of caesium is 55 and its atomic mass is 133. The nucleus of caesium atom therefore contains

A 78 protons and 55 elections
B 55 protons and 78 neutrons
C 55 neutrons 78 electrons
D 78 protons and 55 neutrons

Question 10:

Four elements P,Q, R and S have atomic numbers of 4, 10, 12 and 14 respectively . Which of these electrons is a noble gas?