Lakshya Education MCQs

Question: Which theory has provided an explanation for the law of conservation of mass and the law of definite proportions?
A.Dalton's atomic theory
B.Lavoisier's theory 
C.J.J Thomson's atomic theory
D.Democritus atomic theory
Answer: Option A
: A

Daltons' atomic theory was based on the laws of chemical combinations i.e.,law of conservation of mass and the law of definite proportions. The two postulates which supports the law of combinations are:
  • Atoms combine in the ratio of small whole numbers to form compounds.
  • Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction

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More Questions on This Topic :

Question 1. According to the Dalton, which element does the following symbol represent?

  1.    Hydrogen
  2.    Carbon
  3.    Oxygen
  4.    Iron
Answer: Option A
: A

Dalton was the first scientist to use the symbols for elements in a very specific sense. The symbols are the unique pictorial representation of each element. The given symbol was used for representing the element "hydrogen".
Question 2. In a biogas plant, methane gas (CH4) is produced as a fuel. Find the mass ratio of carbon to hydrogen in methane.
  1.    3:1
  2.    2:1
  3.    1:3
  4.    4:2
Answer: Option A
: A

Mass of one carbon atom = 12u
Mass of each hydrogen atom = 1u
Mass of 4 hydrogenatoms = 4u
Mass ratio of carbonand hydrogen atomsin methane =12:4=3:1
Question 3. Atomicity of oxygen molecule is 1.
  1.    True
  2.    False
  3.    Atomic mole unit
  4.    Atomic measuring unit
Answer: Option B
: B

Atomicity means the number of atoms present in one molecule. Oxygen exists as O2. The atoms in one molecule of oxygen is2. Hence, it is diatomic and the given statement is false.

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