How to find the percent error of SiO2 in an experiment?

Question

The question states that 1.206g of SiO2 is the theoretical amount recovered/used, 1.111g SiO2 is the experimental amount recovered/used, and the total theoretical mass of the overall sample recovered/used is 5.000g? How do I find the percent error with respect to SiO2? My instructor says the answer is 2.6%, but I keep getting 7.9%.

Answer 1

Sorry, I just now saw your comment. The reason 7.9% is wrong is because the theoretical and experimental had different starting masses:

Theoretical SiO2 percent = 1.206/5 = 0.2412

Experimental percent recovered = 1.111/4.488 = 0.247549

abs(0.2412-0.247549)/0.2412 = 0.026 or 2.6%

I hope that helps

Answer 2

For the values given |1.111-1.206|/1.206 is .079. Therefore, there must be something wrong with the given values. What is the point of mentioning th 5.00 grams? Is the 1.206g from a calculation? I'm not sure what recovered/used is about.