In the following reaction, oxygen is the excess reactant. SiCl4 + O2 → SiO2 + Cl2
The table shows an experimental record for the above reaction.

Experimental Record
Trial Starting Amount of SiCl4 Starting Amount of O2 Actual Yield of SiO2
1 120 g 240 g 38.2 g
2 75 g 50 g 25.2 g

a. Calculate the percentage yield for SiO2 for Trial 1. Also, determine the leftover reactant for the trial. Show your work.
b. Based on the percentage yield in Trial 2, explain what ratio of reactants is more efficient for the given reaction.