1) Set up your equation. Multiply 1.67× 10^24 atoms by 1 mol of carbon, and divide by 6.022×10^23 atoms of carbon (Avogadro's number). The atoms cancel out and will give you the answer in mols of carbon (Remember, 1 mol = 6.022×10^23 atoms).
1.67×10^24 atoms of carbon × 1 mol of carbon
6.022×10^23 atoms of carbon
= 0.277317 mol of carbon -> round to 3 sig figs!
Answer = 0.277 mol of carbon