Question

Calculate number of grams in 1.15*10^21 molecules of P2O5

Answer 1

To go from molecules, we first need to convert to moles and then convert to grams.

To convert from molecules to moles, we need to divide by Avogadro's constant.

1.15*10^21 molecules * (1 mole/6.022*10^23 molecules) = 0.0019097 moles

To convert from moles to grams, we need to use the molar mass.

The molar mass of P₂O₅ is (2*30.98)+(5*16.00) = 141.96
You can find the molar mass using the periodic table.

0.0019097 moles * (141.96 grams/1 mole) = 0.2711 grams.

Since we have 3 significant digits in 1.15*10^21, that means our final answer is limited to 3 significant digits.

Your final answer is 0.271 grams.