# Atoms, Molecules and Chemical Arithmetic MCQs Part 22

## Atoms, Molecules and Chemical Arithmetic MCQs

This is continuous series of chemistry MCQs, so in this post we cover 20 MCQs of chapter Atoms, Molecules and Chemical Arithmetic.

Fahrenheit
Absolute
Kelvin

Giga
Nano
Exa
Mega

cm2
cm3
m2
m3

#### MCQ-4. Which one of the following is a physical change :

Burning of carbon in air
Burning of sulphur in air
Conversion of white phosphorus to red phosphorus
corrosion of metals

Lavoisier
Proust
Gay-Lussacs
Dalton

#### MCQ-6. Which pair of compounds illustrate the law of multiple proportions :

H2S and SO2
FeCl2 and FeCl3
CuO and Cu2O
NH3 and NCl3

0.25
2
4
0.65

#### MCQ-8. The Law of Reciprocal proportions can be used to determine :

Atomic weight of a gas
molecular weiht of gases
equivalent weights
all of these

16
32
40
64

27
36
18
9

#### MCQ-11. Which property of element is always a whole number :

Atomic weight
Atomic Number
Atomic Volume
Equivalent Weight

48
24
12
40

#### MCQ-13. Equivalent weight of an acid is _______ whose basicity is 3 :

Molecular Weight/1
Molecular Weight/2
Molecular Weight/3
Molecular Weight/4

6.02×1023
1
5
90

#### MCQ-15. which one of the following has maximum number of atoms :

24 gram of C (12)
56 gram of Fe (56)
26 gram of Al (27)
108 gram of Ag(108)

#### MCQ-16. 18 gram of water contains :

1 gram of hydrogen
2 gram of hydrogen
3 gram of hydrogen
4 gram of hydrogen

22.4 litres
2.24 litres
44.8 litres
4.48 litres

1
2
4
8

arene
alkane
alkene
alkyne

18
36
38
46

## Atomic Weight related Chemical Formulas

·         Atomic Weight of an Element = Weight of an average Atom of that Element/ (1/12)x Mass of an element of C12
·         1 a.m.u. = 1.66×10-24g
·         Atomic Weight = Gram Atomic Weight (GAW)
·          1 Gram Atomic Weight (GAW) of every element contains 6.023×1023 atoms of that element.
·         No. of gram of an element = weight of element in gram/ Gram Atomic Weight (GAW) of that element

### Methods of Determining Atomic Weight

#### i.Dulong and Pettits Method:

Applicable only for solid elements except Be, B, C, Si.
·      Atomic Weight  x Specific Heat = 6.4 (app.)
·      Atomic Weight  (app.) = 6.4/ Specific Heat (in Calories)
·      Exact Atomic Weight = Equivalent Weight x Valency
·      Valency = App. Atomic Weight / Equivalent Weight

#### ii.Vapour Density Method:

Applicable only for those elements whose chlorides are volatile.
·         Valency of the Element = Molecular Weight of Chloride / Equivalent Weight of Chloride
·         Valency of the Element = (2 x V.D. of Chloride) / (Equivalent Weight of Metal + 35.5)
Where, V.D. = Vapour Density
·         Atomic Weight = Equivalent Weight of Metal x Valency

#### iii.Specific Heat Method:

Applicable only for Gases.
·         Cp/Cv for monoatomic gases = 1.66
·         Cp/Cv for diatomic gases = 1.40
·         Cp/Cv for triatomic gases = 1.33
·         Atomic Weight of Gaseous Element = Molecular Weight/ Atomicity
Where, Atomicity is number of atoms present in a molecule of a gaseous element. For example atomicity of Inert Gas is 1, atomicity of Ozone is 3, atomicity of H2 N2 O2 X2 is 2, and atomicity of Sulphur is 8.

#### iv.Volatile Chloride Formation Method:

·         Atomic Weight of the Element = Equivalent Weight (Z) x Valency (x)

#### v.Isomorphism Method:

This method based on law of Isomorphism. According to law of Isomorphism, “Compounds having identical crystal structure have similar constitution and chemical formula”
·         Atomic Weight = Equivalent Weight x Valency
·         Weight of Element A that combines with certain weight of other elements/Weight of Element B that combines with the same weight of other elements = Atomic Weight of A / Atomic Weight of B

## Molecular Weight related Chemical Formulas

·         Molecular Weight = Weight of 1 Molecule of the Substance/ (1/12)x Weight of 1 atom of C12
·         Actual Weight of 1 Molecule = Molecular Weight x 1.66×10-24g

### Methods of Determining Atomic Weight

#### 1.Diffusion Method:

Applicable only for gases.
·

Where,  r1 & r2 is rate of diffusion of gases and M& M2 is Molecular Weight.

#### 2.Vapour Density Method:

Applicable only for gases.
·         Molecular Weight = 2 x Vapour Density

#### 3.Victor Mayer Method:

Applicable only for volatile liquids and solids.
·         Molecular Weight of a substance = 22400 ml of vapour of a substance at STP

## Equivalent Weight related Chemical Formulas

·         No. of Gram Equivalent Weight = Weight of the substance in gram/ Gram Equivalent Weight of the substance
·         Equivalent Weight of an Element = Atomic Weight/ Valency
·         Equivalent Weight of an Acid = Molecular Weight/ Basicity
·         Equivalent Weight of an Base = Molecular Weight/ Acidity
·         Equivalent Weight of a Salt = Formula Weight/ Total Positive or Negative Charge
·         Equivalent Weight of a Reducing Agent = Formula Weight/ No. of electrons lost per molecule or Total change in Oxidation Number
·         Equivalent Weight of an Oxidising Agent = Formula Weight/ No. of electrons gained per molecule or Total change in Oxidation Number
·         Equivalent Weight of Radicals = Formula Weight of Radical/ No. of units of Charge…..