Question

How many C atoms are present in the sample of C3H8 with a mass of 6.21g?

Answer 1

There are 3 atoms of Carbon in 1 molecule of C₃H₈. So there is three times more of Carbon atoms in 1 mole of C₃H₈ (6.022*10²³ molecules). Find the amount of C₃H₈ given:

$\nu = m (C_3H_8)/ M(C_3H_8)$

$\nu = 6.21/44.1 = 0.14 (mol)$

Find the number of C atoms:

N = 0.14 * 6.022 * 10²³ * 3 = 2.53 * 10²³ (u.)

Answer: 2.53 * 10²³ atoms are present in the sample of C₃H₈ with a mass of 6.21g.