Question

How many moles of Na2Cr2O7 contain 14 moles of oxygen atoms?

Answer 1

Answer: The number of moles of the compound are 2 moles.

Step-by-step explanation:

We are given:

Moles of oxygen atom = 14 moles

The chemical formula for the given compound is
`Na_2Cr_2O_7`

In 1 mole of sodium dichromate, 2 moles of sodium atoms, 2 moles of chromium atoms and 7 moles of oxygen atoms are present.

To calculate the moles of compound, we use unitary method:

7 moles of oxygen atoms are present in 1 mole of sodium dichromate.

So, 14 moles of oxygen atoms will be present in
`(1)/(7)* 14=2mol` of sodium dichromate.

Hence, the number of moles of the compound are 2 moles.

Answer 2

The number of moles of sodium dichromate from the number of moles of oxygen atoms can be determined through stoichiometry. Using the molecular formula of the compound, Na2Cr2O7, 1 mole of the compound contains 7 moles of oxygen. Hence, 14 moles O2*(1 mole Na2Cr2O7/ 7 mole O2) is equal to 2 moles Na2Cr2O7.