91Ó°ÊÓ

The Mass of propane=85.5g

The molar mass of propane, ${\mathrm{C}}_3{\mathrm{H}}_8$, is calculated below.

$\begin{array}{c}{\mathrm{M}}_{\mathrm{Ó\neg }}\text{ }\mathrm{of}\text{ }{\mathrm{C}}_3{\mathrm{H}}_8=\text{ }3×\left({\mathrm{M}}_{\mathrm{Ó\neg }}\text{ }\mathrm{of}\text{ }\mathrm{C}\right)+8×\left({\mathrm{M}}_{\mathrm{Ó\neg }}\text{ }\mathrm{of}\text{ }\mathrm{H}\right)\\ =3×\left(12.01\text{ â¶Ä‰}\frac{\mathrm{g}}{\mathrm{mol}}\right)+8×\left(1.01\text{ â¶Ä‰}\frac{\mathrm{g}}{\mathrm{mol}}\right)\\ =44.11\text{ â¶Ä‰}\frac{\mathrm{g}}{\mathrm{mol}}\end{array}$

Multiply the given mass of propane by the reciprocal of its molar mass to get the number of moles.

Moles of propane$=85.5\text{ }\mathrm{g}\text{ â¶Ä‰}{\mathrm{C}}_3{\mathrm{H}}_8\left(\frac{\mathrm{mol}\text{ â¶Ä‰}{\mathrm{C}}_3{\mathrm{H}}_8}{44.11\text{ }\mathrm{g}\text{ â¶Ä‰}{\mathrm{C}}_3{\mathrm{H}}_8\text{ }}\right)$

Therefore, The Moles of propane is$1.94\text{ }\mathrm{mol}\text{ â¶Ä‰}{\mathrm{C}}_3{\mathrm{H}}_8$.

There are 3 moles of C atoms in 1 moles of ${\mathrm{C}}_3{\mathrm{H}}_8$. The number of moles of C atoms in 85.5 g propane is

Moles of C$=\text{ }5.82\text{ }\mathrm{mol}\text{ â¶Ä‰}\mathrm{C}\left(\frac{3\text{ }\mathrm{mol}\text{ â¶Ä‰}\mathrm{C}}{1\text{ }\mathrm{mol}\text{ â¶Ä‰}{\mathrm{C}}_3{\mathrm{H}}_8}\right)$

Moles of C$=5.82\text{ }\mathrm{mol}\text{ â¶Ä‰}\mathrm{C}$

Therefore, Multiply the calculated number of moles of carbon, C, by its molar mass which is $12.01\text{ â¶Ä‰}\frac{\mathrm{g}}{\mathrm{mol}}$.

Mass of C$=5.82\text{ }\mathrm{mol}\text{ â¶Ä‰}\mathrm{C}\left(12.01\text{ â¶Ä‰}\frac{\mathrm{g}}{\mathrm{mol}}\right)$

Mass of C$=69.90\text{ }\mathrm{g}\text{ â¶Ä‰}\mathrm{C}.$

Therefore, The Mass of C is$69.90\text{ }\mathrm{g}\text{ â¶Ä‰}\mathrm{C}.$