Class 9 Science CBSE worksheet for Atoms and Molecules

Fill In The Blanks:-

1. During a chemical reaction, the sum of the _________ of the reactants and products remain unchanged.
2. In a pure chemical compound, elements are always present in a ________ proportion by mass.
3. Clusters of atoms that act as an ion are called __________ ions.
4. In ionic compounds, the charge on each ion is used to determine the ________of tye compound.
5. The Avogadro constant _________ is defined as the umber of atoms in exactly ________ of crbon-12
6. Mass of 1 mole of a substance is called its __________.
7. The abbreviation used for length names of elements are termed as their _______.
8. A chemical formula is also known as a ________.
9. Those ions which are formed from single atoms are called _________.
10. Ionic compounds are formed by the combination between ________ an ______.
11. The valency of an ion is _________ to the charge on the ion.
12. Mole is a link between the __________ and __________.
13. The SI unit of amount of a substance is __________.

True / False:

1. Formula mass of Na₂O is 62 amu.
2. Those particles which have more or less electrons than the normal atoms are called ions.
3. Formula for sulphur dioxide is SO₃.
4. Molar mass of ethyne (C₂H₂) is 26 g/mol.
5. 22 gm of CO₂ consists of 1 mole.
6. Number of molecules in 32 gram of oxygen is 6.02 x 10²³.
7. Water is an atom.
8. Formula for sulphur dioxide is SO₂.
9. Clusters of atoms that act as an ion is called lopyatomic ion.
10. Mass of 1 mole of a substance is called its formula mass.
11. In a pure chemical compound, elements are always present in a definite proportion by mass.

Very Short Answer Questions:

1. Define term mole.
2. What is Avogadro’s umber?
3. What is gram atomic weight?
4. What is the difference between CO₂ and 2CO₂?
5. Name the following compounds PC₃ and SO₂.
6. In the smallest whole-number ratio must N and O atoms combine to make dinitrogen to tetroxide N₂O₄? What is the mole ratio of the elements I this compound?
7. How many moles of sodium atoms correspond to 1.56 x 10²¹ atoms of sodium?
8. What is the relationship between the formula weight of a substance and its molar mass?
9. How many grams of silver are in 0.263 mol of g?
10. How many atoms are 1.00 x 10^-9 g of lead?
11. How many grams of iron are needed to combine with 25.6g of O to make Fe₂O₃?
12. What is the mass of 4 moles of aluminum atoms? ( Atomic mass of AI = 27u)
13. Calculate the mass of 6.022 x 10²² atoms of He.
14. Calculate the number of moles in 3.011 x 10²² molecules of carbon dioxide.
15. A samp0le of 45.8g of H₂SO₄ contains how many moles of H₂O₄?
16. What s the mass in grams of 5 moles of Fe?
17. How many moles of NaCI are present in 20 gm of the substance?
18. How many grams of O is present in 50 gm of CaCO₃?
19. How many grams of CO₂ are present in 0.1 mole CO₂?
20. Describe the difference between the mass of a mole of oxygen atoms (O) and the mass of a mole of oxygen molecules (O₂).
21. What do you understand by the term Formula unit?

ANSWERS

Fill in the blanks:

1. Masses
2. Definite
3. Polyatomic
4. Chemical formula
5. 86.022 x 1023, 12g
6. Molar mass
7. Symbol
8. Molecular formula
9. Simple ins
10. Metal and non- metals
11. Equal
12. Mass of atoms & number of atoms
13. Mole

True / False:

1. True
2. True
3. False
4. True
5. False
6. True
7. False
8. True
9. True
10. False
11. True

 

Class 9 Maths Class 9 Science