Question

Calculate the number of NaBr formula units formed when 50 $NB{r}_3$ molecules and 57 NaOH formula units are made to react?
$2NB{r}_3+3NaOH\to N_2+3NaBr+3HOBr$

• A. 50
• B. 57
• C. 23
• D. 25

Answer 1

The correct option is B 57

We can treat the numbers of molecules or formula units in the exact same manner as we use moles.
Determining the limiting reagent, $2NB{r}_3+3NaOH\to N_2+3NaBr+3HOBr$
2 moles of $NB{r}_3$ reacts 3 moles of NaOH
$\therefore$ 50 moles of $NB{r}_3$ will react with $\frac{3}{2}\times 50=75$ moles of NaOH
$\therefore$ NaOH is the limiting reagent.
Now, 3 moles of NaOH produce 3 moles of NaBr
So, 57 moles of NaOH will produce 57 moles of NaBr
Hence, 57 formula units of NaOH will produce 57 formula units of NaBr