Convert into mole Question 8 from Chapter 3. Atoms And Molecules

(a) 12 g of oxygen gas

(b) 20 g of water

(c) 22 g of carbon dioxide.

Answer: To get the mass of 1 mole of atom of that element, that is, molar mass, we have to take the same numerical value but change the units from 'u' to 'g'.

∴ 1 mole substance = Total Atomic mass of a substance (u)       Or

                             = Total gram atomic mass of substance (g)  Or

                             = Molar Mass

                             = 1 Mole of substance                                Or 

                             =  6.022 × 10²³ in number of particles of that substance

Here required mole of substance  =  Given mass of substance in 'g' ÷ Molar Mass

(a) 12 g of oxygen gas =  Given mass of oxygen in 'g' ÷ Molar Mass of Oxygen

                                 = 12 ÷ 32 

                                 = 0.375 mole of oxygen

(b) 20 g of water = Given mass of water in 'g' ÷ Molar Mass of Water

                         = 20 ÷ 18

                         = 1.11 mole of water

(c) 22 g of carbon dioxide.= Given mass of Carbon Dioxide in 'g' ÷ Molar Mass of Carbon Dioxide

                                      = 22 ÷ 44

                                      = 0.5 mole of carbon dioxide

This is an answered question from Chapter 3. Atoms And Molecules of CBSE Class 9th Science

Check for Complete Exercise Solution for Chapter 3. Atoms And Molecules | CBSE Class 9th Science