Answer:
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(57.0 g B2O3 / (69.6202 g B2O3/mol) x (4mol BCI3 / 2 mol B2O3) = 1.64 mol BC13
(44.7 g C12) / (70.9064 g C12/mol) x (4mol BCI3 / 6mol C12) = 0.42027 mol BC13
(68.8 g C) / (12.01078 G C/mol) x (4mol BCI3 / 3 mol C) = 7.63 mol BCI3
C12 is the limiting reactant.
(0.42027 mol BCI3) X (117 . 170 g BCI3/mol) = 49.2 g BCI3 in theory.
The average mass of the pennies in the sample is 2.16 g.
We have a set of pennies from which 10.00% have an average mass of 2.15 g and 90.00% have an average mass of 2.156 g. The average mass (am) of the whole set is a weighted average, that considers the mass (m) and the percentage (perc) of each group. We can calculate it using the following expression.

The average mass of the pennies in the sample is 2.16 g.
You can learn more about weighted average here: brainly.com/question/18554478