An organic compound has the following composition by mass: C = 40.687%, H = 5.085%, O = 54.228%. Given vapour density = 59, find its molecular formula.

1. C₄H₆O₄

2. C₄H₆O₂

3. C₄H₄O₂

4. None of the above

When 4.77 g of NaCl is mixed with 5.77 g of AgNO₃, AgCl precipitates according to the reaction:

NaCl + AgNO₃ → AgCl↓ + NaNO₃

What is the mass of AgCl precipitated?

1.  11.70 gm.

2.  9.70 gm.

3.  4.86 gm.

4.  2.86 gm.

At standard temperature and pressure (STP), the volume of oxygen required to completely combust 30 ml of acetylene under similar conditions is:

1. 100 ml

2. 75 ml

3. 50 ml

4. 25 ml

What is the volume (in litres) of oxygen at STP required for complete combustion of 32 g of CH₄

(1) 44.8

(2) 89.6

(3) 22.4

(4) 179.2

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

Which of the following quantities would change if Avogadro’s number were changed from 6.022 × 10²³ mol⁻¹ to 6.022 × 10²⁰ mol⁻¹?

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

Find the mass of precipitate formed when 50 mL of 16.9% (w/v) AgNO₃ solution is mixed with 50 mL of 5.8% (w/v) NaCl solution.

(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