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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 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.....


Class 11 Chapter 6 - Thermodynamics

Class 11 Chapter 6: Thermodynamics

System:

            A system is that part of universe in which we made observations is called system.

Surroundings:

            All remaining part of the universe, other than system is called surroundings.
Universe = System + Surroundings

Types of System:

            The system is classified on the basis of movement of energy and matter inside or outside the system. I.e. open system, closed system and isolated system.

     1.     Open System:

A system in which exchange of matter and energy between the system and surroundings take place, is called open system.
Example:- Reaction in open beaker.

     2.     Closed System:

A system in which exchange of energy between the system and surroundings take place but there is no exchange of matter between the system and surroundings takes place, is called closed system.
Example:- Reaction in closed conducting vessel of steel.

     3.     Isolated System:

A system, in which no exchange of matter and energy between the system and surroundings take place, is called isolated system.
Example:- Reaction in isolated vessel like thermos flask.

The state of the system

            In chemistry, the state of thermodynamic system is described by the measurable or macroscopic i.e. bulk properties of the thermodynamic system.
To learn better, if someone asks, how we can describe the state of a gas?
So to answer this question, we describe the state of a gas by getting information about pressure (p), volume (V), temperature (T) and amount (n) etc. of gas.
So, these variables i.e. p, V, T are known as state variables or state functions.
Why these variables (p, V, T) are called state variables or state functions?
These variables are called state variables or state functions because their values depends only on the state of the system and do not depend on how they are reached on that point.

Internal Energy

            Sum of all energies (like chemical, electrical, mechanical etc.) of the system is called internal energy (U) of the system.
Now question is when internal energy of the system changes?
Internal energy of the system changes when,
·        Heat passes into or heat passes out of the system.
·        Work is done on the system or work is done by the system.
·        Matter enters the system or matter leaves the system.

     i.       Work

Before learning about effect of work on internal energy we first understand what is Adiabatic system.

Adiabatic system

            Adiabatic system is a system which does not allow transfer of heat through its boundary; means heat can not enters or leave the system.

Work on adiabatic system

            If 1kJ mechanical work done (case 1) on the system and 1kJ electrical work done (case 2) on the system than change in temperature is same in bath cases.
So, amount of work done on the system produces the same change of state no matter how this work was done.
So,
            U = U2 – U1 = Wad
Where,
            U = internal energy
            U2 = internal energy at state 2 (final state)
U1 = internal energy at state 1 (initial state)
Wad = adiabatic work
Sign of Wad
a.     If Wad is positive, then work is done on the system.
b.     If Wad is negative, then work is done by the system.

      ii.     Heat

What is heat?

The exchange of energy due to difference in temperature is called heat.

If system allows exchange of heat (conducting walls of the system) then change in internal energy depends on amount of heat transfer between system and surroundings at constant volume when no work is done.
So,
            U = q
Where,
            U = internal energy
            q = heat
            Sign of q
a.     q is positive, if heat is transferred from the surroundings to the system.
b.     q is negative, if heat is transferred from the system to surroundings.



Some Basic Concepts of Chemistry Class 11 MCQ

Some Basic Concepts of Chemistry Class 11 MCQ

some basic concepts of chemistry mcq

These are some of the random multiple question answers from Some Basic Concept of Chemistry...

1. If a matter has definite volume and definite shape, then it is :

Solid
Liquid
Gas
All of the Above


2. Mole is SI unit of :

Current
Temperature
Amount of Substance
Luminous intensity



3. A measured temperature is 100 0F on Fahrenheit scale, then what is this reading be on Celsius scale :

11.2 0C

78 0C

102.7 0C

37.8 0C



4. What amount of H­2O produced by combustion of 32 g of CH4 :

36 g
18 g
72 g
90 g


5. How many moles of CH4 is needed to get 44 gram CO2 after combustion :

0.5 mol of Methane
1 mol of Methane
2 mol of Methane
4 mol of Methane


6. Calculate the mass per cent of the solute, when a solution is prepared by adding 4 gram of substance A to 36 gram of water :

10%
20%
30%
40%


7. What is molarity of  NaOH in the Solution, that is prepared by adding 2 gram NaOH in water to get 500 mL of the solution :

0.4 M
1.0 M
0.1 M
4.0 M


8. A measured temperature is 44 0C on Celsius scale, then what is this reading be on Fahrenheit scale :

111.2 0F

88.8 0F

32 0F

199.8 0F



9. Dalton in 1803, gives :

Law of conservation of mass

Law of definite proportion

Law of multiple proportion

Gay Lussac’s law of gaseous volume



10. The prefix 10-15 is :

Atto
Femto
Peta
Tera


View below video on Some Basic Concept of Chemistry Quiz

Also read Chemistry Notes of this chapter at below link...

11 Class Chapter 1- Some Basic Concept of Chemistry Notes


Humidity

What is Humidity?

The simple meaning of humidity is ‘atmospheric moisture’ or ‘amount of water vapor in the atmosphere’.
what is humidity
 Humidity is the amount of water vapors present in the atmosphere (or air). Water vapors are the gaseous state of water and are invisible.
 Humidity can be measured by three ways that are: absolute, relative and specific.
    1.   Absolute humidity is the water content of air in the gram per cubic meter at a given temperature.
     2.   Relative humidity is expressed in percentage, and it measures the current absolute humidity relative to the maximum humidity for that temperature.
    3.   Specific humidity is expressed as the ratio of the mass of the water vapors to the total mass of moist air parcel.

What is Absolute Humidity?

To understand absolute humidity let’s assume you are standing in ground and you collect some air. Now you check that air volume in your chemistry lab and get accurate amount of water vapors in gram. If you collect 1 cubic meter of air volume and it contains 30 gram water vapors than absolute humidity of that ground air is 30 grams per cubic meter. So, now you answer this question i.e. what is absolute humidity.
Absolute humidity (AH) is defined as the total mass (in gram) of water vapor present in a given volume (in cubic meter) of air. Absolute Humidity changes with changes in air temperature and pressure. Absolute humidity is the mass of the water vapors( m H 2 O ) {\displaystyle (m_{H_{2}O})} divided by the volume of the air and water vapor mixture.
AH = m/V
Where, AH = Absolute humidity,
             m = mass of the water vapors( m H 2 O ) {\displaystyle (m_{H_{2}O})},
             V = volume of the air and water vapor mixture.


What is Relative Humidity?

To understand relative humidity let’s assume you are in a building where air absolute humidity is 15 grams per cubic meter at 25 degree Celsius temperature and at 25 degree Celsius temperature highest amount of water vapors is 30 grams per cubic meter (saturated air with water vapors 15 grams per cubic meter). So, now you can calculate relative humidity as follows:
Relative humidity = (15 grams per cubic meter / 30 grams per cubic meter)x100
                            RH = 50%
So, now you answer this question i.e. what is relative humidity.
Relative humidity (RH) is defined as the ratio of the partial pressure of water vapors to the equilibrium vapor pressure of water at a given temperature. If temperature of the atmosphere is lower than relative humidity is higher as cold air (air with low temperature) holds more water vapors (moisture) but, If temperature of the atmosphere is higher than relative humidity is lower as hot air (air with high temperature) holds less water vapors (moisture).

What is Specific Humidity?

To understand specific humidity let’s assume you have an air parcel (air volume or some amount of air) and this parcel contains 10 gram mass of water vapors and total mass of air is 1 kg (including mass of all gases present in air and mass of water vapors) than specific humidity is 10 gram per kilogram. So, now you answer this question i.e. what is specific humidity.
Specific Humidity is defined as the ratio of the mass of water vapors in air to the total mass of the mixture of air and water vapors.
Specific Humidity = mass of water vapor/total mass of air

Difference between Humidity and Relative Humidity

Before going to discuss about “Difference between Humidity and Relative Humidity” we need to understand that what is humidity and what is relative humidity. And to get answer of these two questions just read above paragraph once again if you don’t understand.
Humidity is the amount of water vapors present in the atmosphere (or air). Relative humidity is expressed in percentage, and it measures the current absolute humidity relative to the maximum humidity for that temperature.


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