Test: Laws Of Chemical Combination - Class 9 MCQ

The postulates of Dalton’s Atomic theory that is the result of the law of conservation of mass in the relative numbers and kinds of atoms are constant in a given compound. Atoms cannot be created nor destroyed in a chemical reaction.

The correct answer is D: Both A and B.

- Precipitation Reaction: AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) forms a solid precipitate.
- Double Displacement Reaction: AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) involves the exchange of ions between two compounds.
- Explanation: The given reaction demonstrates both characteristics, forming a precipitate (A) and involving double displacement of ions (B), making it both a precipitation and a double displacement reaction.

Formula mass unit is calculatedin same way as molecular mass.

so,zncl₂
= 65.3 + 35.5 x 2

= 65.3 + 71

= 136.3

• The law of conservation of mass states that in a chemical reaction, the total mass of the reactants equals the total mass of the products.
• This means that matter cannot be created or destroyed, only transformed from one form to another.
• Therefore, the correct statement is that matter is conserved during chemical reactions.
• This principle is fundamental in understanding chemical processes and stoichiometry.

Dalton’s Atomic Theory was given by John Dalton.
According to this theory: -
(a) Matter is made up of invisible particles known as atoms.
(b) The properties of all the atoms of a given element are the same including mass.
(c) Atoms of different elements combine in fixed ratios to form compounds.
(d) Atoms are neither created nor destroyed.
(e) The formation of new products results from the rearrangements of existing atoms.
(f) Atoms of an element are identical in mass, size and properties.

Dalton's atomic theory had several drawbacks, including:

• Atoms of an element have exactly the same mass: Isotopes show that atoms of the same element can have different masses.


• Atoms are indivisible: Atoms can be split into subatomic particles (protons, neutrons, electrons).


• Atoms of different elements have the same masses: This is incorrect; atoms of different elements have distinct masses.

 

Thus, the major drawback is summarized by option B: All of these.

The balancing of chemical equations is based on the law of conservation of mass. 
The law of conservation of mass states that mass can be neither created nor destroyed in a chemical reaction. Total mass of reactants is equal to total mass of products.

• option ( a)( The no. of atoms in a given compound is fixed ) , is a postulate of dalton atomic theory. 
• Option ( c)  ( Atoms can neither be created nor destroyed) is also, a postulate of dalton atomic theory. 
• Option ( d) ( Atoms cannot be divided) , is also a postulate of dalton atomic theory. 

But option ( b) is not a postulate of dalton atomic theory.
 

The decomposition of water (H₂O) into its constituent gases yields 1 gram of hydrogen (H₂) and 8 grams of oxygen (O₂) from 9 grams of water, which aligns with the law of conservation of mass.

According to the Law of Conservation of mass, the total mass of the Reactants must equal the total mass of the products. 

The correct answer is: a. Law of Conservation of Mass

Lavoisier is known for establishing the Law of Conservation of Mass, which states that mass is neither created nor destroyed in a chemical reaction.

The correct answer is: c Temperature and Volume

Charles' Law states that the volume of a gas is directly proportional to its temperature (in Kelvin) when the pressure is held constant.