## Introduction

In order to determine the pH of a 0.15 M acetic acid/0.39 M sodium acetate solution where K_a=1.8 x 10^-5, we must first understand what pH is and how it relates to acids and bases. pH is a scale used to measure how acidic or basic a solution is. A pH of 7 is considered neutral, a pH less than 7 is considered acidic, and a pH greater than 7 is considered basic. The closer the pH is to 0, the more acidic the solution is; the closer the pH is to 14, the more basic the solution is.

In order for us to calculate the pH of our given acetic acid/sodium acetate solution, we need to know the concentration of both acids and bases in the solution. In this case, our solution contains 0.15 M acetic acid (HA) and 0.39 M sodium acetate (NaCH_3COO). To find the concentration of hydronium ions (H_3O^+) in our solution, we can use the K_a expression for acetic acid:

K_a = [H_3O^+][A^-]/[HA]

where [A^-] is the concentration of acetate anions (CH_3COO^-) in our solution. We can rearrange this expression to solve for [H_3O^+]:

[H_3O^+] = [HA]*K_a/[A^-] = 0.15M*1.8*10^-5M/0.39M = 2.82*10^-5 M

Now that we know the concentration of hydronium ions in our solution, we can calculate the pH using the following equation:

pH = -log([H_3O^+]) = -log(2.82*10^-5) = 4

## What is pH?

pH is a measure of the acidity or basicity of a solution. It is measured on a scale from 0 to 14, with 0 being the most acidic, 7 being neutral, and 14 being the most basic. A solution with a pH of 4 is 10 times as acidic as one with a pH of 5 and 100 times as acidic as one with a pH of 6.

## The pH Scale

Most people are familiar with the term “acid”, but many do not know that there is a scientific scale that is used to measure the acidity of a substance. This scale is called the pH scale, and it ranges from 0 to 14. A pH of 7 is neutral, a pH less than 7 is acidic, and a pH greater than 7 is alkaline.

The pH of a solution can be measured with a pH meter, which will give a readout of the acidity or basicity of the solution on the pH scale. To determine the pH of a particular solution, one must first understand how to calculate it. The following steps can be followed to calculate the pH of a given solution:

1) Determine the molarity of the acid and base in the solution. This can be done by looking at the molarity of the dissolution or by using a graduated cylinder to measure the volume and then using molality to calculate molarity.

2) Use the Henderson-Hasselbalch equation to calculate pH. This equation takes into account both the molarity of the acid and base as well as their dissociation constants.

pH = pKa + log10([A-]/[HA])

Where:

pH = acidity or basicity of solution on pH scale

pKa = dissociation constant of acid

[A-] = concentration of conjugate base in solution

[HA] = concentration of weak acid in solution

3) Once you have calculated pH using the Henderson-Hasselbalch equation, you can use this value to determine whether your solution is acidic, basic, or neutral. A pH less than 7 is considered acidic, while a pH greater than 7 is considered basic. A neutral solution will have a pH equal to 7.

## How to Measure pH

There are many ways to measure pH, but the most common way is with a pH meter. A pH meter is a device that measures the acidity or alkalinity of a solution. To use a pH meter, you simply place the electrode in the solution and read the pH on the display.

pH meters are very sensitive, so it is important to calibrate them before each use. To calibrate a pH meter, you will need to have two solutions of known pH values, one acidic and one basic. These solutions can be purchased from a scientific supply store.

Once your pH meter is calibrated, you can use it to measure the pH of any solution, including acetic acid-sodium acetate solutions. To measure the pH of a 015 M acetic acid-039 M sodium acetate solution, simply place the electrode in the solution and read the pH on the display.

## How to Calculate pH

First, calculate the concentration of the acid in moles per liter (mol/L) using the formula:

Concentration of acid (mol/L) = Molarity x Volume (L)

where

Molarity (M) is the concentration of the acid in moles per liter, and

Volume (V) is the volume of the acid in liters.

Next, calculate the concentration of the base in moles per liter (mol/L) using the formula:

Concentration of base (mol/L) = Molarity x Volume (L)

where

Molarity (M) is the concentration of the base in moles per liter, and

Volume (V) is the volume of the base in liters.

Now that you have both concentrations, you can use one of the following formulas to calculate pH:

```
pH = -log[H3O+] OR pH = pKa + log[Base]/[Acid]
where [H3O+] is the concentration of hydrogen ions in mol/L, pKa is -log(Ka), [Base] is the concentration of conjugate base in mol/L, and [Acid] is concentration of conjugate acid in mol/L.</p><br /><h2>Conclusion</h2><br /><p>
```

In conclusion, to determine the pH of a 015 m acetic acid039 m sodium acetate solution where ka18 x 105, we first need to find the [H3O+]. This is done by taking the negative log of the concentration of hydronium ions. We then need to use the Henderson-Hasselbalch equation to solve for pH.