The percentage of copper in a copper(II) salt can be determined by using a thiosulphate titration. 0.305 gm of a copper(II) salt was dissolved in water and added to, an excess of potassium iodide solution liberating iodine according to the following equation 2Cu² (aq) + 4I^– (aq) $\stackrel{}{\rightleftharpoons }$ 2CuI(s) + I₂(aq) The iodine liberated required 24.5cm³ of a 0.100 mole dm^-3 solution of sodium thiosulphate 2S₂O₃^2- (aq) + I₂(aq) $\underset{}{\overset{}{\to }}$ 2I^– (aq) + S₄O₆^2- (aq) the percentage of copper, by mass in the copper(ll) salt is. [Atomic mass of copper = 63.5]

1. 64.2

2. 51.0

3 48.4

4. 25.5

Oxygen contains 90% O¹⁶ and 10% O¹⁸. Its atomic mass is

(1) 17.4

(2) 16.2

(3) 16.5

(4) 17

The total number of electrons present in 1.6 gm. of methane is [IIT 1976; Roorkee 1985; CPMT 1987, 92]

(1) 6.02 × 10²³

(2) 6.02 × 10²²

(3) 6.02 × 10²¹

(4) 4.02 × 10²⁰

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

4.4 g of an unknown gas occupies 2.24 litres of volume at NTP. The gas may be: 

The number of gram molecules of oxygen in 6.02 × 10²⁴ CO molecules are:

1. 10 g molecules

2. 5 g molecules

3. 1 g molecules

4. 0.5 g molecules

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

1. 1.8 g

2. 18 g

3.  3.6 g

4.  36 g

The number of moles of BaCO₃ which contains 1.5 moles of oxygen atoms is:

1. 0.5

2. 1

3. 3

4. 6.02 ×10²³

The oxide of metal contains 40% by mass of oxygen. The percentage of chlorine in the chloride of the metal is

1. 84.7

2. 74.7

3. 64.7

4. 44.7