# Calculating pH of Water After Adding HCl and NaOH

• thercias
In summary, to calculate the pH of water after adding HCl and NaOH, you can determine the concentration of each compound and use the Henderson-Hasselbalch equation or a pH meter. The purpose of adding HCl and NaOH to water is to adjust the pH for specific experiments or industrial processes. The concentration of HCl and NaOH can be determined through titration. When handling these chemicals, it is important to take safety precautions such as wearing protective gear and working in a well-ventilated area. The pH of water can change significantly after adding HCl and NaOH, depending on the concentrations of the acid and base.
thercias

## Homework Statement

What will the pH be by adding 1M HCL and 1M NaOH to pure water?

pH= -log[H+]

## The Attempt at a Solution

Well, If we form the reaction formula we get
HCl + NaOH ---> H20 + NaCl

This is a neutralizing reaction, so the net effect produces just water. Therefore the pH doesn't change. Is this logic right?

Correct.

Depends on whether you are expected to take ionic strength of the solution into effect, or not. That's typically at least undergraduate level though.

And don't forget the question was: what is the pH?

Yes, your logic is correct. The addition of equal amounts of 1M HCl and 1M NaOH to pure water will result in a neutralization reaction, producing only water and a salt (NaCl). Since the concentration of H+ ions and OH- ions will be equal, the pH of the resulting solution will remain neutral at a pH of 7. This can also be calculated using the equation pH = -log[H+], where [H+] is equal to 10^-7 for a neutral solution.

## 1. How do I calculate the pH of water after adding HCl and NaOH?

To calculate the pH of water after adding HCl and NaOH, you first need to determine the concentration of each compound. Then, you can use the Henderson-Hasselbalch equation (pH = pKa + log([A-]/[HA])) to calculate the pH based on the concentrations of the acid and its conjugate base. Alternatively, you can use a pH meter to directly measure the pH of the solution.

## 2. What is the purpose of adding HCl and NaOH to water?

HCl and NaOH are commonly used to adjust the pH of water. HCl is an acid, so adding it to water will decrease the pH, making the solution more acidic. NaOH is a base, so adding it to water will increase the pH, making the solution more basic. This can be useful in various experiments or industrial processes where a specific pH is required.

## 3. How do I determine the concentration of HCl and NaOH in the solution?

The concentration of HCl and NaOH can be determined by performing a titration. This involves adding a known volume of the acid or base to a solution of known concentration until the solution reaches a neutral pH. The amount of acid or base added can then be used to calculate the concentration of the unknown solution.

## 4. Are there any safety precautions I should take when handling HCl and NaOH?

Yes, both HCl and NaOH are corrosive substances and should be handled with caution. Wear appropriate protective gear, such as gloves and goggles, when handling these chemicals. It is also important to work in a well-ventilated area to avoid inhaling any fumes.

## 5. Can the pH of water change after adding HCl and NaOH?

Yes, the pH of water can change significantly after adding HCl and NaOH, depending on the concentrations of the acid and base. For example, adding a small amount of HCl to water can decrease the pH from 7 (neutral) to around 2 (very acidic). Similarly, adding a small amount of NaOH can increase the pH from 7 to around 12 (very basic).

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