\[ \text{Si} + 2\text{Cl} \rightarrow \text{SiCl}_4 \]Is this equation balanced? No! Why? Because the problem, as posted, is incorrect. Chlorine gas must be diatomic: Cl_2. After doing that, the equation is balanced. From here, use the coefficient ratios for mole ratios and it should be easy. Note, from the balanced equation, 2 moles of chlorine are required to form 1 mole of SiCl_4. If you still need help, let me know. I'll complete the solution for you. :D