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Atoms and Molecules CBSE Class 9

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Atoms and Molecules Topics

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Question 1/20

Q 1. An atom is 16 times heavier than 1/12th of the mass of the carbon atom (C-12 isotope). The mass in a.m.u. is 

Solution

An atom is 16 times heavier than 1/12th of the mass of the carbon atom (C-12 isotope). The mass in a.m.u. is 16. 

Q 2. Ammonia is a …………. molecule. 

Solution

Ammonia is a tetratomic molecule. 

Q 3. Which among these was a first person to recognize a workable distinction between the fundamental particle of an element and compound? 

Solution

John Dalton was a first person to recognize a workable distinction between the fundamental particle of an element and compound 

Q 4. Which of the following elements has relative atomic mass of 14? 

Solution

The relative atomic mass of nitrogen is 14. 

Q 5. A water samples from lake, ocean, rain or pond have the ratio of mass of hydrogen to oxygen in water is 1:8; this is illustrated by 

Solution

Water samples from lake, ocean, rain or pond have the ratio of mass of hydrogen to oxygen in water is 1:8;this is illustrated by Law of definite proportion 

Q 6. 1 nanometre = ……… metre 

Solution

1 nanometre = 10-9 metre 

Q 7. What is the black compound formed on silverware? 

Solution

The black compound formed on silverware is silver sulphide. 

Q 8. Who named the indivisible particle of matter as an atom? 

Solution

Democritus named the indivisible particle of matter as an atom. 

Q 9. What is the atomicity of the Fe molecule? 

Solution

The atomicity of the Fe molecule is 1. 

Q 10. Which of the following elements is a monatomicmonoatomic gas? 

Solution

Ne is a monoatomic gas. 

Q 11. How many atoms of hydrogen are present in the hydrogen molecule? 

Solution

Two atoms of hydrogen combine to form the hydrogen atom. 

Q 12. What is the relative atomic mass of oxygen? 

Solution

The relative atomic mass of oxygen is 16. 

Q 13. Who proposed the law of definite proportions? 

Solution

Joseph Proust proposed the law of definite proportions. 

Q 14. The ……………. is the smallest particle of an element or compound capable of independent existence. 

Solution

The molecule is the smallest particle of an element or compound capable of independent existence. 

Q 15. Name the smallest particle of a substance which has independent existence. 

Solution

The molecule is the smallest particle of a substance which has independent existence. 

Q 16. Find the major drawback of Dalton’s theory 

Solution

the major drawback of Dalton’s theory is atoms are indivisible. Atom is further divided into protons, neutrons and electrons. 

Q 17. Carbon reacts with oxygen forms CO and CO2 in the ratio of 12:16 and 12:32. These figures show 

Solution

Carbon reacts with oxygen forms CO and CO2 in the ratio of 12:16 and 12:32. These figures show law of multiple proportional. 

Q 18. The number of atoms present in potassium dichromate K2Cr2O7 is 

Solution

The number of atoms present in potassium dichromate K2Cr2O7 is 11. 

Q 19. The noble gases are found in the nature as a 

Solution

The noble gases are found in the nature as a single atom, as they are monoatomic in nature. 

Q 20. Which of the following is a symbolic representation of its composition of a compound? 

Solution

Chemical formula is a symbolic representation of the composition of a compound. 

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