A radioactive substance disintegrate its 90% in 100 days. How much time it will take to disintegrate its 99.9% ?

• 100 days

• 200 days

• 300 days

• 400 days

Which of the following has magnesium?

• Haemoglobin

• Chlorophyll

• Vitamin B₁₂

• Haemocyanin

Pure nitrogen gas is obtained from

• NH₃ + NaNO₂

• NH₄Cl + NaNO₂

• N₂O + Cu

• (NH₄)₂Cr₂O₇

The Modern Periodic Table is based on the properties of elements as a function of

• atomic number

• atomic mass

• electronegatvity

• electron affinity

The pH of 0.05 M solution of a strong dibasic acid is

• 0.0

• 1.0

• 0.2

• 0.5

Which of the following represents the first law of thermodynamics?

• $∆$U = q + W

• $∆$U = p . $∆$V

• $∆\mathrm{U} = ∆\mathrm{H} + \mathrm{P}.∆\mathrm{V}$

• $∆$H = q + W

What number of subshells are possible in n = 3 energy level?

• 7

• 8

• 9

• 6

For the equilibrium reaction,

2SO₂ (g) + O₂ (g) $\rightleftharpoons$ 2SO₃ (g) + $∆$H

the increase in temperature

• favours the formation of SO₃

• favours the decomposition of SO₃

• does not affect the equilibrium

• stops the reaction

What is the electronic configuration of O^2- ion?

• 1s², 2s², 2p⁵, 3s¹

• 1s², 2s², 2p⁴, 3s²

• 1s², 2s², 2p⁶

• 1s², 2s², 2p⁴

An organic compound containing C, H and N gives the following on analysis : C = 40%, H = 13.33% and N = 46.67%. What would be its empirical formula?

• C₂H₇N

• C₂H₇N₂

• CH₄N

• CH₃N