Tag: atoms, molecules and chemical reactions

Quizzes (12) Questions (3)

Questions Related to atoms, molecules and chemical reactions

Multiple choice chemistry atoms, molecules and chemical reactions law of constant proportion - i law of constant proportion law of definite proportions

Which of the following is a limitation of the law of constant composition is not applicable?

  1. When same isotopes of an element take part in the formation of a particular compounds.

  2. When different isotopes of different elements take part in the formation of a particular compound.

  3. When different isotopes of an element take part in the formation of a particular compound.

  4. None of the above.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Law of constant composition is not applicable if an element exists in different isotopes which may be involved in the formation of the compound. The elements may combine in the same ratio but the compounds formed may be different.

Hence, the correct option is $(C)$
Multiple choice chemistry atoms, molecules and chemical reactions law of constant proportion - i law of constant proportion law of definite proportions
Assertion (A): Pure water obtained from different sources such as a river, well, spring, the sea always contains hydrogen and oxygen in the ratio of 1:8 by mass.

Reason (R): The total mass of reactants and products during chemical or physical change is always the same.

  1. Both A and R are true and R is the correct explanation of A

  2. Both A and R are true and R is not correct explanation of A

  3. A is correct and R is incorrect

  4. A is incorrect and R is correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Assertion states the law of definite proportions, which is true for pure water regardless of source. Reason states the law of conservation of mass, which is also a true chemical principle. However, the constant composition by mass is not explained by the conservation of mass during reactions.

Multiple choice chemistry atoms, molecules and chemical reactions law of constant proportion - i law of constant proportion law of definite proportions

Statement: Every nine parts of water by weight contain eight parts by weight of oxygen. 


State whether the given statement is true or false.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water (H2O) has a molar mass of 18 g/mol (2*1 + 16). The mass ratio of oxygen to water is 16/18, which simplifies to 8/9. Thus, 9 parts of water contain 8 parts of oxygen.