What is the total number of atoms in 3 g of ethane C2H6?

Given:
m (C2H6) = 3 g
NA = 6.02 * 10 ^ 23 mol − 1

To find:
N (atoms C2H6) -?

Decision:
1) Calculate the molar mass of C2H6:
M (C2H6) = 30 g / mol;
2) Calculate the amount of substance C2H6:
n (C2H6) = m (C2H6) / M (C2H6) = 3/30 = 0.1 mol;
3) Calculate the number of C2H6 molecules:
N (C2H6 molecules) = n (C2H6) * NA = 0.1 * 6.02 * 1023 = 6.02 * 10 ^ 22;
4) Calculate the number of C2H6 atoms:
N (atoms C2H6) = N (molecules C2H6) * N (atoms in 1 molecule C2H6) = 6.02 * 10 ^ 22 * 8 = 4.82 * 10 ^ 23.

Answer: The number of C2H6 atoms is 4.82 * 10 ^ 23.