Question

A sample of C₃H₈ has 2.40 * 10²⁴ atoms.

How many carbon atoms does the sample contain?

? C atoms

What is the total mass of the sample?

? g C₃H₈

Answer 1

The question should be A sample of C3H8 has 2.4*1024​ H atoms. Then it can be calculated.

there are 3 C atoms for every 8 H atoms.

So, 2.4 X 10²⁴ H atoms X (3 C / 8 H) = 0.9 X10²⁴ C atoms

To get to the mass of the sample, one need to calculate the number of moles of C3H8 in the sample, and then use the molar mass of C3H8 to calculate the mass in grams,

2.4 X 10²⁴ H atoms X (1 molecule C3H8 / 8 H atoms) X 1 mole C3H8 / 6.02X10²³ molecules) = 0.498 moles C3H8

Molar mass of C3H8 = 44 g/mol

0.498 moles C3H8 X 44 g/mol = 21.91 grams C3H8