Question

A .calculate the no.of given atoms of hydrogen present in one dozen molecule of hydrogen gas.convert the given number of hydrogen in terms of no of moles.B.if hydrogen combines with oxygen in ratio of 1:8 by mass to form water, how many moles of oxygen in ratio of 1:8 by mass to form water,how many moles of oxygen would be required for the given amount of hydrogen gas ?

Answer 1

No. of molecules in one dozen =12
No. of atoms of hydrogen present in 12H₂ molecule =12*2=24 H atoms

6.023*10²³ molecules =1 mole of H2 molecules
1 Molecule =1/(6.023*10²³) Moles of H2

12 molecules of H₂ =12/6.023*10²³ moles =2 *10^-23 moles

B) Law of constant proportion states- ‘A chemical compound always contains same elements combined together in the same proportion by mass'.
Reaction for the formation of water:
H₂ + ½ O₂ → H₂O
Molar mass of H₂ =2g
Molar mass of 1/2O2= 16 g
Ratio in which hydrogen and oxygen combines =2g/16g =1/8

C) 1 Mole of hydrogen combines = 1/2 Mole of oxygen
2*10^-23 moles of hydrogen combines = 1*10^-23 moles of oxygen