Question

How many grams are in 2.5 moles of Carbon

Answer 1

Carbon's atom mass is 12. So 1 mole of Carbon is 12 grams. We should multiply
12 by 2.5:
$2.5\quad =\quad \frac { 5 }{ 2 } \\ 12\cdot \frac { 5 }{ 2 } \\ \frac { 60 }{ 2 } \\ 30$

Answer 2

According to the periodic table, carbon's molar mass is 12.011 grams per mole (that's the small number under the element).  So, just multiply like this to get the answer:

$(2.5\ mol\ C)(\frac{grams\ C}{12.011\ mol\ C})=0.20814\ g\ C$

So, there are approximately 0.208 grams in 2.5 moles of carbon.