An organic compound contains carbon, hydrogen, and oxygen.
Its elemental analysis gave C, 38.7%, and H, 9.67%.
The empirical formula of the compound would be:

1. CH₃O                                   

2. CH₂O

3. CHO                                     

4. CH₄O

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

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

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

When 22.4 L of H₂ (g) is mixed with 11.2 L of Cl₂ (g), each at STP, the moles of HCl(g) formed is equal to:

1. 1 mole of HCl (g)

2. 2 moles of HCl (g)

3. 0.5 mole of HCl (g)

4. 1.5 mole of HCl (g)

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)

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

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.

A mixture of gases contains H₂ and O₂ gases in the ratio of 1:4 (w/w). What is the molar

ratio of the two gases in the mixture?

1. 1:4             

2. 4:1             

3. 16:1               

4. 2:1