1. Tungsten carbide (WC), used in making tools and jewelries, is produced by the reaction of tungsten hexachloride (WCl6), H2 and CH4 at 670℃.

WCl6 + H2 + CH4 WC + 6HCl

If 23.5 g WCl6 reacts with excess H2 and CH4, and 10.8 g WC are recovered, what is the percent yield?