# Question #9fe3d

May 7, 2016

$0.2 M$

#### Explanation:

There are two methods you can use to solve this problem.

First method:

Since the two solutions neutralize each other then we can use the equation

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

Where ${C}_{1}$ is the concentration of $K O H$, ${V}_{1}$ is the volume of $K O H$ and ${V}_{2}$ is the volume of $H N {O}_{3}$.

Substitute the values into the equation.

$\left(0.15 M\right) \left(10 m L\right) = \left({C}_{2}\right) \left(7.5 m L\right)$
$1.5 = \left({C}_{2}\right) \left(7.5\right)$
${C}_{2} = 0.2 M$

Second Method:

This is essentially a longer version of method 1 but I find that it works well in actually fostering understanding, rather than just taking the shortcut.

To do this, you first need to find the no. of moles in the solution for which you know both concentration and volume. In this case, $K O H$.

Using $M = \frac{n \setminus m o l}{V}$, $0.15 M = \frac{n \setminus m o l}{0.01 L}$

$= 0.0015 m o l$ The number of moles in the base solution and acid solution are equal.

Using the same formula, $M = \frac{0.0015 \setminus m o l}{0.0075 L}$

$M = 0.2$