You were wrong.
Finding the limiting reagent if 39.9 grams of SiO2 were reacted with 77.4 grams of H2F2.
SiO2+2H2F2=>SiF4+2H2O
First we find the GFW of each reactant.
GFW of SiO2: 60
GFW of H2F2: 70
Next we divide the number of grams of each reactant by the GFW.
39.9/60= 0.665
77.4/70= 1.105
Finally, we multiply each of the results by the coefficient of the other reactant/
0.665 x 2= 1.33
1.99 x 1= 1.105
Because 1.33 is smaller than 1.105, we know that the limiting reagent is SiO2.
SiO2+2H2F2=>SiF4+2H2O
First we find the GFW of each reactant.
GFW of SiO2: 60
GFW of H2F2: 70
Next we divide the number of grams of each reactant by the GFW.
39.9/60= 0.665
77.4/70= 1.105
Finally, we multiply each of the results by the coefficient of the other reactant/
0.665 x 2= 1.33
1.99 x 1= 1.105
Because 1.33 is smaller than 1.105, we know that the limiting reagent is SiO2.