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.

MCQ-1.  What is SI unit of temperature :

  Fahrenheit
  Centigrade
  Absolute
  Kelvin

MCQ-2.  Prefix 10¹⁸ is :

  Giga
  Nano
  Exa
  Mega

MCQ-3.  Derived SI Unit of Area is :

  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

MCQ-5.  Law of Multiple Proportions was proposed by which of the following scientist :

  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

MCQ-7.  The ratio of the rates of the diffusion of a given element to that of helium is 4. what is the molecular weight of the element :

  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

MCQ-9.  The specific heat of a metal is 0.16 , its approximate atomic weight would be _____________ :

  16
  32
  40
  64

MCQ-10.  Atomic weight of a trivalent element of equivalent weight 9 is_____ :

  27
  36
  18
  9

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

  Atomic weight
  Atomic Number
  Atomic Volume
  Equivalent Weight

MCQ-12.  A metallic oxide contains 60% of the metal. The equivalent weight of the metal is ________ :

  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

MCQ-14.  90 gram of water contains how many moles :

  6.02x10²³
  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

MCQ-17.  volume of 4.4 gram of carbon di oxide at STP is________ :

  22.4 litres
  2.24 litres
  44.8 litres
  4.48 litres

MCQ-18.  Avogadro Number of Helium atom weighs ______ gram :

  1
  2
  4
  8

MCQ-19.  A hydrocarbon containing 86% carbon. 448 mL of the hydrocarbon weighs 1.68 gram at STP, Then hydrocarbon is an __________ :

  arene
  alkane
  alkene
  alkyne

MCQ-20.  The % of nitrogen in urea is about________ :

  18
  36
  38
  46

Chemistry formulas for Atoms, Molecules and Chemical Arithmetic Part I

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. = 1.66x10^-24g

·         Atomic Weight = Gram Atomic Weight (GAW)

·          1 Gram Atomic Weight (GAW) of every element contains 6.023x10²³ 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 1.66x10^-24g

Methods of Determining Atomic Weight

1.              Diffusion Method: 

                                          Applicable only for gases.

 ·         

Where,  r₁ & r₂ is rate of diffusion of gases and M₁ & 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.....

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