Tag: chemistry

Questions Related to chemistry

Which of the following is a postulate of Dalton's atomic theory?

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. All matter consists of indivisible particles called atoms

  2. The atom is the smallest unit of matter that can take part in a chemical reaction

  3. Atoms of same element can combine in more than one ratio to form two or more compounds

  4. All of the above

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Correct Option: D

Dalton's theory of same element have same mass and properties was proved wrong with the invention of:

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. molecules

  2. isotopes

  3. neutrons

  4. compounds

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Correct Option: B
Explanation:

According to Dalton Atomic Theory, atoms of an element are identical in mass, size and many other chemicals or physical properties. 


But, practically we observe that atoms of several elements differ in their densities and masses. 

These atoms with the different masses are known as isotopes. For example, Chlorine (Cl) has 2 isotopes with the mass numbers of 35 and 37.

Hence, the correct option is $\text{B}$

A/An______ is the smallest particle of a substance which can take part in a chemical reaction.

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. atom

  2. molecule

  3. both A and B

  4. none of the above

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Correct Option: A
Explanation:

An atom is the smallest particle of a substance which can take part in a chemical reactions.

Various theories were put forth to study the nature of atom. The main postulates of Dalton's atomic theory are :

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. all matter are composed of atoms

  2. all matters are composed of molecules

  3. all atoms of an element are identical.

  4. the atoms of different elements vary in size and mass.

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Correct Option: A,C,D
Explanation:

It was John Dalton who firstly developed a theory on the structure of matter, later on which is known as Dalton's atomic theory.


DALTON'S ATOMIC THEORY :

1. Matter is made up of very small undivisible particle called atoms.
2. All the atoms of a given element is identical in all respect i.e. mass, shape, size, etc.
3. Atoms cannot be created nor destroyed by any chemical process.
4. Atoms of different elements are different in nature.

Dalton suggested that atoms were indestructible and unchangeable to explain:

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. why mass is conserved in chemical reactions.

  2. why elements combine in fixed weight ratios to form compounds.

  3. why elements are characterized by the mass of their atoms.

  4. why compounds combine in fixed weight ratios in chemical reactions.

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Correct Option: A
Explanation:

Atoms cannot be subdivided, created or destroyed into smaller particles when they are combined,separated or rearranged in chemical reactions. The whole matter remains conserved in the form of reactants changing to products.

Which of the following is not a postulate of Dalton's atomic theory? 

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. Different elements have atoms of different masses.

  2. Atoms combine in simple whole number ratios to form compounds..

  3. Atoms are not created or destroyed in chemical change.

  4. Atoms of a single element can have different masses.

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Correct Option: D
Explanation:

Postulates of Dalton's atomic theory:

  • All matter consists of indivisible particles called atoms.
  • Atoms of the same elements are similar in shape and mass but differ from the atoms of other elements.
  • Atoms cannot be created or destroyed.
  • Atoms of different elements may combine with each other in a fixed, simple, whole number ratios to form compound atoms.
  • The atom is the smallest unit of matter that can take part in a chemical reaction.

Dalton said that elements are distinguished from each other by :

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. the charge on their ions

  2. the density of their solid forms

  3. the weights of their atoms

  4. the shapes of their atoms

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Correct Option: C
Explanation:

Atoms of a given element are identical in size, mass and other properties, while atoms of different elements differ in size, mass and other properties.

Who was the first scientist which proposed that "Matter is made up of indivisible particles called atoms"?

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. Lavoiser

  2. Dalton

  3. Thomson

  4. Faraday

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Correct Option: B
Explanation:

Dalton Atomic theory postulates-

All matter is made up of atoms and atoms are indestructible cannot be created or destroyed so the total mass of reactants remains equal to the total mass of products.

Atoms of different elements combine in :

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. unequal ratios.

  2. prime number ratios.

  3. equal ratios.

  4. whole number ratios.

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Correct Option: D
Explanation:

When elements react, their atoms combine in simple, whole-number ratios.   By suggesting that compounds contained characteristic atom-to-atom ratios, Dalton effectively explained the law of definite proportions.

Dalton's atomic theory was not accepted fully :

chemistry atoms, molecules and radicals history of atomic model atomic theory of dalton daltons atomic theory

  1. when atoms combine It must be presumed to be a binary one, unless some cause appear to the contrary.

  2. when elements react, their atoms sometimes combine in more than one simple, whole-number ratio.

  3. elements are characterized by the mass of their atoms.

  4. None of the above

Show answer
Correct Option: A
Explanation:

According to Dalton, When atoms combine in only one ratio, ".. it must be presumed to be a binary one, unless some cause appear to the contrary". 

          There was no experimental evidence to support this postulate, and it lead him to mistakenly assume that the formula of water was OH and the formula of ammonia was NH. As a result, Dalton's atomic weights for oxygen and nitrogen were incorrect and his experimental data did not support many of the conclusions he drew from it.