# topic: Chemical Arithmatic

1

Q:

In a mole of water vapour at STP, the volume actually occupied or taken by the molecules (i.e., Avogadro’s No.Volume of one molecule) is

(a) :  Zero
(b) :  Less than 1% of 22.4 litres
(c) :  About 10% of the volume of container
(d) :   1% to 2% of 22.4 litres
(e) :  Between 2% to 5% of 22.4 litres

Answer:  Less than 1% of 22.4 litres
Explanation:

Q: (a) :  1, 1, 2, 2, 1
(b) :  2, 2, 1, 1, 1
(c) :   2, 1, 1, 2, 1
(d) :  2, 2, 1, 2, 1

Q:

Zinc sulphate contains 22.65% of zinc and 43.9% of water of crystallization. If the law of constant proportions is true, then the weight of zinc required to produce 20 g of the crystals will be

(a) :  45.3 g
(b) :  4.53 g
(c) :  0.453 g
(d) :  453 g

Q:

Irrespective of the source, pure sample of water always yields 88.89% mass of oxygen and 11.11% mass of hydrogen. This is explained by the law of

(a) :  Conservation of mass
(b) :  Constant composition
(c) :   Multiple proportions
(d) :  Constant volume

Explanation:  H2O contains H and O in a fixed ratio by mass. It illustrates
the law of constant composition.

Q:

A 100 ml solution of 0.1 n HCl was titrated with 0.2 N NaOH solution. The titration was discontinued after adding 30 ml of NaOH solution. The remaining titration was completed by adding 0.25 N KOH solution. The volume of KOH required for completing the titration is

(a) :  70 ml
(b) :   32 ml
(c) :  35 ml
(d) :   16 ml

Q:

If 10 21 molecules are removed from 200mg of CO2 , then the number of moles of CO2 left are

(a) :  2.85 ×10^-3
(b) :   3 28.8 ×10^-3
(c) :  3 0.288 × 10^-3
(d) :   1.68 × 10^-2

Q:

10 3 dm of 2 N gas and 10 3 dm of gas X at the same temperature contain the same number of molecules. The gas X is

(a) :  CO
(b) :  2 CO
(c) :  2 H
(d) :  NO

Q:

One litre hard water contains 12.00 mg Mg2+ milli equivalent
of washing soda required to remove its hardness is

(a) :  1
(b) :  12.15
(c) :  1× 10^-3
(d) :  12.15 ×10^-3

Q:

What volume of Hydrogen gas, at 273 K and 1 atm pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8) from the reduction of boron trichloride by Hydrogen

(a) :  22.4 L
(b) :  89.6 L
(c) :  67.2 L
(d) :  44.8 L