Atoms And Molecules Class 9 Chemistry Worksheet Pdf
Class 9 Chemistry students should refer to the following printable worksheet in Pdf for Atoms And Molecules in standard 9. This test paper with questions and answers for Grade 9 Chemistry will be very useful for exams and help you to score good marks
Class 9 Chemistry Worksheet for Atoms And Molecules
CBSE Class 9 Chemistry Worksheet - Atoms And Molecules - Practice worksheets for CBSE students. Prepared by teachers of the best CBSE schools in India.
ATOMS AND MOLECULES
1. Name the scientist who gave two important laws of chemical combination.
2. What is law of conservation of mass? Describe with an activity.
3. State the law of constant proportion. Give example.
4. Write the postulates of Dalton’s atomic theory.
5. What is the difference between 2N and N2?
6. What is the difference between an atom and molecule?
7. If 100g of water is decomposed, how many grams of oxygen and hydrogen are obtained?
8. Write symbols of: (a) copper (b) mercury (c) iron (d) silver (e) gold (f) argon (g) zinc (h) cobalt (i) lead (j) potassium (k) silicon
9. What is meant by valency of an element?
10. Give two examples each of:
(a) Mono atomic molecule (b) tri atomic molecule (c) Di atomic molecule (d) poly atomic molecule
11. Write the chemical formula of: (a) Sodium oxide (b) calcium chloride (c) aluminium oxide
(d) magnesium hydroxide (e) sodium carbonate
12. Find the mass of
(a) .2 moles of oxygen gas
(b) 1.5 moles of water
(c) 3 moles of neon
(a) .5 moles of sodium (e) 2 moles of nitrogen element
13. Find the molecular mass of:
14. How many moles are there in 200 g of Na?
15. Calculate the mass of 1 atom of nitrogen?
16. How many molecules are present in 10 g of H2O?
17. Find the formula unit mass of:
Exam Questions NCERT Class 9 Science Chapter 3 Atoms And Molecules
Question. What is meant by the term chemical formula?
Ans : The chemical formula of a compound is a symbolic representation of its composition and actual number of atoms in one molecule of a pure substance may be an atom or a compound
Question. How was the relative atomic mass determined?
Ans : Relative atomic masses were determined by using the laws of chemical combinations and the compound formed.
Question. What is the number of electrons in Mg atom and Mg2+ ion?
Ans : Mg = 12e–
Mg2+ = 10e–
Question. Define valency.
Ans : The combining power of an element to attain the noble gas configuration is called valency. Or, it is defined as number of electrons lost or gained by an atom to acquire noble gas configuration.
Question. Name the instrument which produces image of the surface of element that shows atoms.
Ans : Scanning tunnelling microscope.
Question. The relative atomic mass of oxygen atom is 16. Explain its meaning.
Ans : The relative atomic mass of an atom is the average masses of the atom, as compared to th 12 1 the mass of one carbon-12 atom.
Question. Why atoms form ions?
Ans : Atoms get stability by acquiring the stable electronic configuration of the nearest noble gas for which either they lose electrons or gain electrons and thus acquire noble gas configuration.
Question. Write the postulate given by the Indian philosopher Maharishi Kanad.
Ans : Indian philosopher Maharishi Kanad postulated if we divide matter we will get smaller and smaller particles. He said that a time will come when we come across smallest particles beyond which further division will not be possible.
Question. Who was the first scientist to give the concept of formation of compounds?
Ans : Antoine L. Lavoisier gave the concept of formation of compounds.
Question. Define the term gram atom. How is it related to mole and Avogadro number?
Ans : The atomic mass of an element expressed in grams is called gram atomic mass. One gram atom of any element contains 6.022 × 1023 atoms of the element. It is equal to one mole of atoms. One gram atomic mass = 6.022 × 1023 atoms = 1 mole
Question. Name the gas which gives the lightest positively charged particle.
Ans : Hydrogen.
Question. 50 g of 10% lead nitrate is mixed with 50 g of 10% sodium chloride in a closed vessel. It was found after reaction that 6.83 g of lead chloride was precipitated. Besides, the reaction mixture contained 90 g water and sodium nitrate. Calculate the amount of sodium nitrate formed.
Ans : 50 g of 10% lead nitrate = 5 g lead nitrate
+ 45 g water
50 g of 10% sodium chloride = 5 g sodium chloride
+ 45 g water
Total content before reaction = 5 + 5 + 90 = 100
Total content after reaction = 90 g
Amount of precipitate = 6.83 g
According to law of conservation,
Total mass of reaction mixture = 100 g
Amount of sodium nitrate = 100 – 90 – 6.83 = 3.17 g
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