I need help with Chemistry

Question

unbelievabledreams · Answer

Chromium metal can be produced by the reduction of Cr2O3 with elemental silicon:
2 Cr2O3 + 3 Si right-arrow 4 Cr + 3 SiO2
If 350.0 grams of Cr2O3 are reacted with 235.0 grams of elemental silicon, 213.2 grams of chromium metal are recovered. What is the percent yield?

photon336 · Answer

In our reaction we have to figure out how many moles were produced by doing the stoichiometry and then figure out how many grams of Cr would be recovered. this is our theoretical yield, I believe, because it's how many grams we should get based primarily on the math. 

However, sometimes you get less than what you expected, due to experimental error. so that's why the % yield tells you in a way how good your reaction was.

so it's $$\frac{ What you get from your experiment }{ what you should have had from stiochiometry }$$

photon336 · Answer

translates to experimental/theoretical x 100 = % yield

unbelievabledreams · Answer

Yes, I got it. But I felt like I am receiving a wrong answer. 

350.0g Cr2O3 = 1 mol/60.09g = 4 mol Cr / 3 mol Si = 28.09g/ 1mol 

Is that correct?

photon336 · Answer

Take a look at this and see how I did it

photon336 · Answer

Cr2o3 molar mass is 152g/mol

photon336 · Answer

The % yield is always used in reactions like copper sulfate, and sometimes things happen that lower your yield, ie not heating your compound long enough in that case.

unbelievabledreams · Answer

I got it. Thank you.

photon336 · Answer

No problem! Yeah just balance your equations and look for the limiting reagent. Once you do those two things it's really easy after that.