Avogadro Number or Avogadro constant is the number of particles (atoms, ions or molecules) present in one mole of a substance. The unit of the Avogadro constant is mol^-1. It is denoted as N_A and is equal to 6.022 × 10²³ mol⁻¹.

1. 6.022 × 10²³ atoms of carbon are present in

(a) 12 moles

(b) 6 moles

(c) 1 mole

(d) 4 moles

2. Find the number of atoms in 12 g of Mg, if there are x number of atoms in one mole of carbon.

(a) 0.5x

(b) x

(c) 1.5x

(d) 2x

3. The phosphorus molecule contains

(a) 3 x 6.022 × 10²³

(b) 2 x 6.022 × 10²³

(c) 4 x 6.022 × 10²³

(d) 6.022 × 10²³

4. According to The International Committee for Weights and Measures, one mole is the amount of substance present in

(a) 1 gram of any metal

(b) 12 grams of any metal

(c) 12 grams of carbon-12 (¹²C)

(d) 1 gram of carbon-12 (¹²C)

5. If the Avogadro Number is changed from 6.022 × 10²³ to 6.022 × 10²⁰, then it would change

(a) the ratio of chemical species to each other in a balanced equation

(b) the mass of one mole of carbon

(c) the definition of mass in units of grams

(d) the ratio of elements to each other in a compound

6. How many grams of O is present in 1.5 moles of oxygen?

(a) 16 g

(b) 9.03 x 10²³ g

(c) 6.02 x 10²³ g

(d) 24 g

7. Avogadro Number is represented by

(a) A_o

(b) M_a

(c) N_A

(d) A_N

8. Find the number of valence electrons in 4.2 g of N₃^– ion.

(a) 4.2 N_A

(b) 2.1 N_A

(c) 3.2 N_A

(d) 1.6 N_A

9. Which of the following has a mole ratio 1:1?

(a) 7 g of N and 12 g of Na

(b) 20 g of Na and 20 g of Ca

(c) 14 g of N and 24 g of Mg

(d) 10 g of Ca and 6 g of C

10. How many particles are present in one mole of any substance?

(a) 6.022 × 10²²

(b) 6.022 × 10²³

(c) 6.022 × 10²¹

(d) 6.022 × 10²⁴

Answer