# How many milliliters of 0.125 M Ba(OH)2(aq) must be used to produce 5.5 moles of water? Please balance the equation before solving the problem.

May 31, 2018

You must use 22 L of the barium hydroxide solution.

#### Explanation:

There are three steps involved in this stoichiometry problem:

1. Write the balanced chemical equation
2. Use the molar ratio from the balanced equation to calculate the moles of ${\text{Ba(OH)}}_{2}$
3. Calculate the volume of ${\text{Ba(OH)}}_{2}$

Step 1. Write the balanced chemical equation.

Let's assume you are using $\text{HCl}$ as the acid.

${M}_{r} : \textcolor{w h i t e}{m m m m m m m m m m m m m m m l l} 18.02$
$\textcolor{w h i t e}{m m m} \text{Ba(OH)"_2 + "2HCl" →"BaCl"_2 + "2H"_2"O}$

Step 2. Calculate the moles of ${\text{Ba(OH)}}_{2}$

The molar ratio from the balanced equation is

$\text{Ba(OH)"_2:"H"_2"O} = 1 : 2$.

${\text{Moles of Ba(OH)"_2 = 5.5 color(red)(cancel(color(black)("mol H"_2"O"))) × ("1 mol Ba(OH)"_2)/(2 color(red)(cancel(color(black)("mol H"_2"O")))) = "2.75 mol Ba(OH)}}_{2}$

Step 3. Calculate the volume of ${\text{Ba(OH)}}_{2}$

${\text{Volume of Ba(OH)"_2 = 2.75 color(red)(cancel(color(black)("mol Ba(OH)"_2))) × ("1 L Ba(OH)"_2)/(0.125color(red)(cancel(color(black)("mol Ba(OH)"_2)))) = "22 L Ba(OH)}}_{2}$