# Question 83f4d

Apr 4, 2017

You need $\text{0.17 L}$ of the $\text{12.0 M}$ solution.

#### Explanation:

Molarity (M) is a unit of concentration in solutions. If a solution has a molarity of 2, we would identify it as 2M, and we say it is 2 molar. M means mol/L. So a 2M solution has a concentration of 2 mol/L.
The formula that allows you to answer this question is:

${M}_{1} {V}_{1} = {M}_{2} {V}_{2}$

where ${M}_{1}$ and ${M}_{2}$ are the molarity of the solutions in mol/L, and ${V}_{1}$ and ${V}_{2}$ are the volume of the solutions in liters.

Known
${M}_{1} = \text{12.0 mol/L}$
${M}_{2} = \text{1.0 mol/L}$
${V}_{2} = \text{2.0 L}$

Unknown : ${V}_{1}$

Solution
Rearrange the equation to isolate ${V}_{1}$. Substitute the known values into the equation and solve.

${V}_{1} = \frac{{M}_{2} {V}_{2}}{M} _ 1$

V_1=(1.0color(red)cancel(color(black)("mol"))/color(red)cancel(color(black)("L"))xx2.0"L")/(12.0color(red)cancel(color(black)("mol"))/color(red)cancel(color(black)("L"))#$=$$\text{0.17 L}$ rounded to two significant figures