A steel wire weighing 6 g was burned in oxygen. This formed 0.1 g of carbon oxide.

A steel wire weighing 6 g was burned in oxygen. This formed 0.1 g of carbon oxide. Calculate the mass fraction of carbon in steel. 

Given:
m (steel) = 6 g
m (CO2) = 0.1 g

To find:
ω (C) -?

Decision:
1) Write the reaction equation:
C + O2 => CO2 ↑;
2) Calculate the amount of carbon dioxide substance:
n (CO2) = m (CO2) / M (CO2) = 0.1 / 44 = 0.002 mol;
3) Determine the amount of carbon substance:
n (C) = n (CO2) = 0.002 mol;
4) Calculate the mass of carbon:
m (C) = n (C) * M (C) = 0.002 * 12 = 0.024 g;
5) Calculate the mass fraction of carbon:
ω (C) = m (C) * 100% / m (steel) = 0.024 * 100% / 6 = 0.4%.

Answer: The mass fraction of C is 0.4%.