Oxygen consists of two isotopes:

\(O ^{16}\) with 90% natural abundance
\({O}^{18}\) with 10% natural abundance
 

Calculate the average atomic mass of oxygen based on its isotopic composition:

1. 17.4

2. 16.2

3. 16.5

4. 17

KClO₃ on heating decomposes to KCl and O₂. The volume of O₂ at STP liberated by 0.1 mole KClO₃ is:

1. 4.36 L

2. 3.36 L

3. 2.36 L

4. None of these

At S.T.P. the density of CCl₄ vapour in g/L will be nearest to [CBSE PMT 1988]

(1) 6.84

(2) 3.42

(3) 10.26

(4) 4.57

A 4.4 g sample of an unknown gas occupies a volume of 2.24 L at NTP. Identify the gas from the following options:

1. Carbon dioxide

2. Carbon monoxide

3. Oxygen

4. Sulphur dioxide

The mass of carbon present in 0.5 mole of K₄[Fe(CN)₆] is:

The number of moles of oxygen in one litre of air containing 21% oxygen by volume under standard conditions is [CBSE PMT 1995]

(1) 0.186 mole

(2) 0.21 mole

(3) 0.0093 mole

(4) 2.10 mole

The empirical formula of an organic compound containing carbon and hydrogen is CH₂. The mass of one litre of this organic gas is exactly equal to that of one litre of N₂. Therefore, the molecular formula of the organic gas is:

An organic compound consists of carbon, hydrogen, and nitrogen. Upon elemental analysis, it is found to contain 40% carbon, 13.3% hydrogen, and 46.67% nitrogen by mass. Determine the empirical formula of the compound.

1. CHN

2. C₂H₂N

3. CH₄N

4. C₂H₇N

The volume of oxygen at STP required to completely burn 30 ml of acetylene at STP is [Orissa JEE 1997]

(1) 100 ml

(2) 75 ml

(3) 50 ml

(4) 25 ml

If Avogadro number N_A, is changed from 6.022 x 10²³ mol^-1 to 6.022 x 10²⁰ mol^-1 this would change

(1) the definition of mass in units of grams

(2) the mass of one mole of carbon

(3) the ratio of chemical species to each other in a balanced equation

(4) the ratio of elements to each other in a compound