Question

How many moles are in 15.62g of P?

Answer 1

`\boxed {\boxed {\sf 0.5043 \ mol \ P}}`

Step-by-step explanation:

To convert from moles to grams, we must use the molar mass. This is found on the Periodic Table. Look for Phosphorous or P.

• Phosphorus (P): 30.973762 g/mol

We can use this number as a ratio.

`(30.973762 \ g \ P )/(1 \ mol \ P)`

Multiply by the given number of grams: 15.62

`15.62 \ g \ P *(30.973762 \ g \ P )/(1 \ mol \ P)`

Flip the fraction so the grams of phosphorus cancel.

`15.62 \ g \ P *(1 \ mol \ P)/(30.973762 \ g \ P )`

`15.62 *(1 \ mol \ P)/(30.973762 )`

`(15.62 \ mol \ P)/(30.973762 )`

Divide.

`0.504297799 \ mol \ P`

The original measurement of grams has 4 significant figures, so our answer must have the same.

For the number we calculated, that is the ten thousandth place. The 9 in the hundredth thousandth place tells us to round the 2 to a 3.

`0.5043 \ mol \ P`

There are 0.5043 moles of phosphorus in 15.62 grams.