# Calculating pH of Mixed Solutions: HCl and Sodium Acetate, Acetic Acid and NaOH

• pari786
In summary, to calculate the final pH of the given solutions, we need to use the equation pH = pKa = log (salt/acid). For part a), we can find the number of moles of salt, sodium acetate, and use stoichiometric calculations to find the concentration of acid. For part b), we can use similar calculations and assume a stoichiometric reaction to determine the pH.
pari786

## Homework Statement

Calculate the final pH of the following solutions:
a) 65.0 ml of 0.105 M HCl and 100 ml of 0.118 M sodium acetate solutions are mixed.
b) 100 ml of a 0.109 M acetic acid and 100 ml of a 0.123 ml NaOH solution are mixed.

## Homework Equations

pH = pKa = log (salt/acid)

## The Attempt at a Solution

for part a) i found the no.of moles of salt sodium aceate

0.118 mol/L x 0.1 L = 0.0118 mol

then after that I don't know how to fing the concentration of acid ... and if I know I can do the rest of the part a) using stoichiometric caluclations ... please help me with it

for part b) the same problem

I need immediate help beause this is due in 5 hours ... please do something about it

1. Just assume acetate is stoichiometrically protonated by the strong acid.

2. There is an excess of base - so there is no buffer solution. Once again, assume reaction (neutralization) was stoichiometric. pH is determined by the excess base alone.

## 1. What is the formula for calculating pH of a mixed solution?

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

## 2. How do you calculate the concentration of hydrogen ions in a mixed solution?

To calculate the concentration of hydrogen ions in a mixed solution, you will need to know the concentrations of all the individual components (HCl, sodium acetate, acetic acid, and NaOH) as well as their respective dissociation constants. Then, use the Henderson-Hasselbalch equation: pH = pKa + log([salt]/[acid]), where pKa is the dissociation constant for the acid, [salt] is the concentration of the salt, and [acid] is the concentration of the acid.

## 3. Can you provide an example calculation for pH of a mixed solution?

Let's say we have a mixed solution with 0.1 M HCl, 0.05 M sodium acetate, 0.05 M acetic acid, and 0.2 M NaOH. The dissociation constant for acetic acid (CH3COOH) is 1.8x10^-5. Using the Henderson-Hasselbalch equation, we can calculate the concentration of hydrogen ions as follows: pH = 4.74 + log(0.05/0.05) = 4.74. Therefore, the pH of this mixed solution is 4.74.

## 4. What is the importance of calculating pH in mixed solutions?

Calculating pH in mixed solutions is important because it helps us understand the acidity or basicity of a solution, which is crucial in various scientific fields such as chemistry, biology, and environmental science. It also allows us to determine the concentration of certain chemical species present in the solution, which can have implications for reactions and processes occurring in the solution.

## 5. Are there any limitations to using the Henderson-Hasselbalch equation for calculating pH of mixed solutions?

Yes, there are some limitations to using the Henderson-Hasselbalch equation. It assumes that the acid and its conjugate base are in equilibrium, which may not always be the case in a real-world mixed solution. Additionally, it does not take into account the activity coefficients of the ions in the solution, which can affect the accuracy of the calculated pH.

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