Test: Laws Of Chemical Combination


20 Questions MCQ Test Science Class 9 | Test: Laws Of Chemical Combination


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QUESTION: 1

A student heats 25g of reactant ‘A’ with 50g of reactant ‘B’. He obtains 50g of product ‘C’ and recovers 25 g of unreacted ‘B’. Which of the following law is confirmed in the following reaction?

Solution: Two laws are followed in this question.
First law is Law of definite proportion as follows: 
Here 25 g of reactant A reacts with 50 g of reactant B to produce 50 g of product C. That means 25 g of A consumes only 25 g of B. The ratio is 1:1. Even if there would have been say 75 g B is present, still only 25 g of B will react with 25 g of A. Or if 10 g of B is present then only 10 g of A will react and remaining 15 g of A will remain unreacted. 
Second law is Law of conservation of mass as follows :
There is 25 g of A and 50 g of B. That means total 75 g of reactant is present. On product side 50 g of C and 25 g of unreacted B is present. That means total 75 g of product is present. Hence, the correct option will be " Law of conservation of mass and Law of constant proportion ".
QUESTION: 2

Law of conservation of mass can be derived from which postulate of Dalton’s atomic theory?

Solution:

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.

QUESTION: 3

5 grams of compound A reacts with 10 grams of compound B to produce a new compound C. What should be the mass of C according to law of conservation of mass?

Solution: As from law of conservation of mass:-mass of reactants=mass of product Therefore, mass of compound A + mass of compound B=mass of compound C So, 5g + 10g= 15g
QUESTION: 4

According to Law of conservation of mass, mass of reactants wil be equal to the mass of:

Solution: Law of conversation of mass:in a chemical reaction mass of reactants must be equal to the mass of products because atoms r neither created nor destroyed in a chemical reaction. This was proposed by Antoine lavoisier but experimentally proved by landolt.
QUESTION: 5

The reaction used in the experiment to verify the law of conservation of masses is included in which of the following categories?

Solution:
QUESTION: 6

The atomic masses and chemical properties of Sulphur and Phosphorus are different. This can be explained on the basis of:

Solution:
QUESTION: 7

When CaCO3 is heated, it forms CaO and CO2. Which of these statements best describes the mass of the products if 100 g of CaCO3 is heated

Solution:
QUESTION: 8

Calculate the formula unit mass of ZnCl2?

Solution:
Formula mass unit is calculatedin same way as molecular mass.
so,zncl2= 65.3+35.5 x 2
             = 65.3+71
            =136.3
QUESTION: 9

Which of the following statements is true about the law of conservation of mass?

Solution:
QUESTION: 10

Which of the following statements is true about the law of conservation of mass?

Solution:

Law of conservation of mass states that mass can neither be created nor be destroyed in a chemical reaction. Or we can say that the total mass present in LHS must be equal to the RHS.

QUESTION: 11

Who gave the Law of constant proportions?

Solution:
A molecule of water will always have two hydrogen atoms and one oxygen atom, meaning that in a bottle of pure water the hydrogen to oxygen atom ratio will always be 2:1. This seems very logical to us today. But 300 years ago, scientists didn't understand compounds this way. However, in 1794, Joseph Proust published the Law of Constant Proportions, which says that a chemical molecule will always contains the same elements in the same proportion.
There are two parts to the law of constant proportions: 1) there will always be the same elements that make up a compound, and 2) the mass of these compounds will always be in the same proportion.
QUESTION: 12

Which of the following statement is not in accordance with Dalton’s atomic theory?

Solution:

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.

QUESTION: 13

Which of the following is the major drawback of Dalton’s atomic theory?

Solution: According to Dalton’s atomic theory, matter is indivisible, i.e., which cannot be divided. But now it is known that under special circumstances, atoms can be divided into still smaller particles called electrons, protons and neutrons. This was the major drawback of Dalton's atomic theory of matter.
QUESTION: 14

Which of the following is correct for the ‘Law of Conservation of Mass’?

Solution: Law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction....

It was proposed by Antoine lavoisier but experimentally proved by landolt
QUESTION: 15

The balancing of chemical equation is based upon:

Solution:

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.

QUESTION: 16

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

Solution:
  • 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.
 

QUESTION: 17

Which type of reaction is being used in the experiment of verifying the law of conservation of mass?

Solution: According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants. The law of conservation of mass is useful for a number of calculations and can be used to solve for unknown masses, such the amount of gas consumed or produced during a reaction.
QUESTION: 18

9 grams of water decompose to give:

Solution:
QUESTION: 19

Who stated the Law of conservation of mass?

Solution:
QUESTION: 20

If all the reactants in a chemical reaction are completely used, which of the following statements accurately describes the relationship between the reactants and the products?

Solution:

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

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