If the 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.

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide

and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate

in the sample? (Atomic weight of Mg = 24)

1. 75

2. 96

3. 60

4. 84

When 50 mL of a 16.9 %  (w/v) solution of AgNO₃ is mixed with 50 mL of 5.8% (w/v) NaCl solution, then the mass of precipitate formed is:

(Ag = 107.8, N = 14, O = 16, Na= 23,Cl=35.5)

The number of water molecules is maximum in -

1. 18 molecules of water

2. 1.8 g of water

3. 18 g of water

4. 18 moles of water

25.3 g of Sodium carbonate Na₂CO₃ is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, Na⁺ and carbonate ion ${\mathrm{CO}}_3^{2-}$ are respectively (Molar mass of Na₂CO₃ = 106 g mol^-1)

1. 0.955 M and 1.910 M

2. 1.910 M and 0.955 M

3. 1.90 M and 1.910 M

4. 0.477 M and 0.477 M

The number of atoms in 0.1 mole of a triatomic gas is: 
(N_A=6.02 x10²³mol^-1)

10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. The amount of water produced in this reaction will be:

1. 2 mol

2. 3 mol

3. 4 mol

4. 1 mol

How many moles of lead (II) chloride will be formed from a reaction between 6.5g of PbO and 3.2g of HCl?

(1) 0.044                           

(2) 0.333

(3) 0.011                           

(4) 0.029

Concentrated aqueous sulphuric acid is 98% ${\mathrm{H}}_2{\mathrm{SO}}_4$ by mass and has a density of 1.80 g mL^-1. Volume of acid required to make one litre of 0.1 M H₂S0₄ solution is :

(1) 11.10 mL

(2) 16.65 mL

(3) 22.20 mL

(4) 5.55 mL

What is the molarity of ${\mathbf{H}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}$ solution that has a density 1.84 g/cc at $\mathbf{35}\mathbf{°}\mathbf{C}$ and contains 98% ${\mathbf{H}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}$ by weight?

1. 4.18 M                                   2. 8.14 M

3. 18.4 M                                   4. 18 M