Find the simplest formula of a compound that's found to contain 32.38 g of Na, 22.65 g of S and 44.99 g of O. Find the empirical formula.  

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t-nez | High School Teacher | (Level 3) Associate Educator

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The emprical formula is the simplest whole number ratio of moles of each element in a compound. To get this ratio we need to convert the amount of each element from grams to moles by dividing by the molar mass:

32.38g Na x 1 mole/22.99g = 1.408 moles Na

22.65g S x 1 mole/32.06g = 0.7065 moles S

44.99g O x 1 mole/16.00g = 2.812 moles O

Now divide each mole amount by the smallest to get whole numbers:

1.408/0.7065 = 1.99 = 2 moles Na

0.7065/0.7065 = 1 mole S

2.812/0.7065 = 3.98 = 4 moles O

The empirical formula is `Na_2SO_4`

If you are solving a problem in which the last step does't produce integers, multiply each number obtained in the last step by a whole number that will produce integers. For example, if you get 1.5 moles of a substance multiply each amount by 2.

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