Atoms and Molecules Worksheet

Given below are the Class 9 Science CBSE worksheet for Atoms and Molecules
(a) Short questions
(b) True and False problems
(c) Fill in the blank's
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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 $Na_2O$ 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 $SO_3$.
  4. Molar mass of ethyne ($C_2H_2$) is 26 g/mol.
  5. 22 gm of $CO_2$ consists of 1 mole.
  6. Number of molecules in 32 gram of oxygen is $6.02 \times 10^{23}$.
  7. Water is an atom.
  8. Formula for sulphur dioxide is $SO_2$.
  9. Clusters of atoms that act as an ion is called polyatomic 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 Number?

3.What is gram atomic weight?

4. What is the difference between $CO_2$ and $2CO_2$?

5. Name the following compounds $PC_3$ and $SO_2$.

6. In the smallest whole-number ratio must N and O atoms combine to make dinitrogen to tetroxide $N_2O_4$? What is the mole ratio of the elements in this compound?

7.How many moles of sodium atoms correspond to $1.56 \times 10^{21}$ 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 $1.00 \times 10^{-9}$ g of lead?

11.How many grams of iron are needed to combine with 25.6g of O to make $Fe_2O_3$?

12.What is the mass of 4 moles of aluminium atoms? ( Atomic mass of AI = 27u)

13.Calculate the mass of $6.022 \times 10^{22}$ atoms of He.

14.Calculate the number of moles in $3.011 \times 10^{22}$ molecules of carbon dioxide.

15.A sample of 45.8g of $H_2SO_4$ contains how many moles of $H_2SO_4$?

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 $CaCO_3$?

19.How many grams of $CO_2$ are present in 0.1 mole $CO_2$?

20.Describe the difference between the mass of a mole of oxygen atoms (O) and the mass of a mole of oxygen molecules ($O_2$).

21.What do you understand by the term Formula unit?


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