# How Do You Calculate the pH of a Sodium Ethanoate Solution?

• josephcollins
In summary, the person is asking for help with calculating the pH of a solution of sodium ethanoate, given the pKa of ethanoic acid/ethanoate ions. They explain their method of using the Ka to find the concentration of H+ ions, but there may be more unknown concentrations in the system. They also request clarification on whether they should be using ethanoic acid or ethanoate.
josephcollins
Hi ppl. I have a question. I'm given the pka of ethanoic acid/ethanoate ions at 4.75 and i have to work out the ph of a 5*10^-2 moldm3 solution of sodium ethanoate. I worked it out by getting the Ka from 10^-4.75 and then saying that the concentration of Ch3COO- in the dissociation of ethanoic acid is also 5*10^-2 moldm3. Then i used the equation for the Ka to get the corresponding concentration of H+ ions in this dissociation and hence the ph, is this method of reasoning correct? Thanks, Joe

The question itself seems to indicate an initial concentration of ethanoate, however, your discussion implies ethanoic acid? Please be more clear...

## 1. What is the formula for calculating the pH of CH3COONa?

The formula for calculating the pH of CH3COONa is pH = -log[H+], where [H+] is the concentration of hydrogen ions in the solution.

## 2. How do I determine the concentration of hydrogen ions in a solution of CH3COONa?

The concentration of hydrogen ions can be determined using the dissociation constant (Ka) of CH3COONa, which is 1.8 x 10^-5 at 25°C. The formula is [H+] = √(Ka*[CH3COONa]).

## 3. Can I use a pH meter to measure the pH of CH3COONa?

Yes, a pH meter can be used to measure the pH of CH3COONa. However, it is important to calibrate the pH meter using standard solutions of known pH values before use.

## 4. How does the pH of CH3COONa change when diluted with water?

When CH3COONa is diluted with water, the concentration of hydrogen ions decreases, leading to an increase in pH. This is because the dissociated ions of CH3COONa can interact with water molecules, reducing the number of free hydrogen ions in the solution.

## 5. What is the range of pH values for a solution of CH3COONa?

The pH range for a solution of CH3COONa is from about 8-9, making it slightly basic. This is due to the presence of the acetate ion, which is a weak base and can act as a buffer to maintain a constant pH in the solution.

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