# A 311.86 gram sample of a substance is found to consist of 35.23% manganese,35.89% oxygen, and 28.88% water.  What is the formula and name of this substance?

Posted on

To solve for the formula of the compound, first we have to know the mass of the unknown substance. We let substance x (unknown) be 311.86 grams.

Out of 311.86 grams of x:

`311.86 * (35.23)/(100) = 109.868 grams Mn`

`311.86 * (35.89)/(100) = 111.927 grams O`

`311.86 * (28.88)/(100) = 90.065 grams H2O`

From the mass of the components, we can get their mole equivalent using the molar mass.

`109.868 grams Mn * (1 mol e Mn)/(54.938 grams Mn)`

= 1.9999 moles = 2

`111.927 grams O * (1 mol e O)/(15.999 grams O)`

= 6.9955 moles O = 7

`90.065 grams H2O * (1 mol e H2O)/(18.015 grams H2O)`

= 4.9995 moles H2O = 5

Finally, we can use the whole number mole equivalent and write the molecular formula of the compound.

`Mn2O7*5(H2O)`

This compound is known as Manganese heptoxide pentahydrate. The IUPAC name for this compound is Manganese(VII) oxide pentahydrate.

Sources:

We’ve answered 320,488 questions. We can answer yours, too.