How many moles of hydrogen fluoride will react with 5.90 moles of silicon dioxide to produce silicon tetrafluoride?

Nov 24, 2015

$\text{23.6 moles HF}$

Explanation:

The key to this problem is the balanced chemical equation for this reaction.

Hydrogen fluoride, $\text{HF}$, will react with silicon dioxide, ${\text{SiO}}_{2}$, to produce silicon tetrachloride, ${\text{SiF}}_{4}$, and liquid water according to the following chemical equation

$\textcolor{red}{4} {\text{HF"_text((g]) + "SiO"_text(2(s]) -> "SiF"_text(4(g]) + 2"H"_2"O}}_{\textrm{\left(l\right]}}$

Notice that you have a $\textcolor{red}{4} : 1$ mole ratio between hydrogen fluoride and silicon dioxide.

This tells you that regardless of how many moles of silicon dioxide take part in the reaction, the reaction will always consume $\textcolor{red}{4}$ times more moles of hydrogen fluoride.

In your case, you need to know how many moles of hydrogen fluoride will be needed to react completely with $5.90$ moles of silicon dioxide.

To react completely simply means that all the moles of silicon dioxide must be consumed in the reaction.

So, use the aforementioned mole ratio to get

5.90color(red)(cancel(color(black)("moles SiO"_2))) * (color(red)(4)" moles HF")/(1color(red)(cancel(color(black)("mole SiO"_2)))) = color(green)("23.6 moles HF")