Question
Mon March 26, 2012 By: Priyanshi Tyagi

what is the number of atoms present in 0.05g of water?

Expert Reply
Mon March 26, 2012

The molar mass of water (H2O) is 18.0 grams/mol (1.008 + 1.008 + 16.0). This means there is one mole of water in 18.0 grams. One mole contains 6.022 × 1023 atoms/molecules/ions. 

So,
0.05g / 18.01528g/mol = 0.0028mol. 

The ratio of hydrogen and oxygen in H2O is 2:1, which means, there are 

 

  • 0.0056mol of hydrogen

and 

 

  • 0.0028mol of oxygen.

There are 6.022 x 1023 particles per mole. 
Number of hydrogen atoms: 

 

0.0056mol x 6.022x1023mol-1 = 33.7x1020 

Number of oxygen atoms: 

 0.0028mol x 6,02214179x1023mol-1 =16.9x1020




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