# Calculating pH Change from HClO4 Addition

when you add 10.0 mL of 1.0M HClO4 into 990.0mL water, the pH changes by 2.
how would you find the change in pH?

1. Write out the expression that defines pH
2. Assume HClO4 is close to 100% dissociated in solution
3. From the original concentration of HClO4, find [H+] and calculate the original pH from this

4. Calculate the new (diluted) concentration of HClO4 (molarity = number of moles/volume of solution)
5. Using the new value of [H+], calculate pH again.
6. Subtract from the original number to find the difference.

## 1. How do you calculate the pH change when adding HClO4?

To calculate the pH change, you will first need to know the initial pH and the concentration of the acid. Then, you can use the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), to determine the new pH after adding HClO4. The change in pH can be calculated by subtracting the initial pH from the new pH.

## 2. What is the role of HClO4 in changing pH?

HClO4 is a strong acid, meaning it dissociates completely in water. When it is added to a solution, it increases the concentration of H+ ions, causing the solution to become more acidic and resulting in a decrease in pH.

## 3. How does the concentration of HClO4 affect the pH change?

The concentration of HClO4 directly affects the pH change. The higher the concentration of the acid, the more H+ ions are added to the solution, resulting in a larger change in pH.

## 4. What is the significance of the pKa value in calculating pH change?

The pKa value represents the acid's strength and is a measure of its ability to donate H+ ions. In the Henderson-Hasselbalch equation, the pKa is used to determine the ratio of the conjugate base ([A-]) to the acid ([HA]), which affects the pH of the solution.

## 5. Are there any factors that can affect the accuracy of pH calculations when using HClO4?

One factor that can affect the accuracy is the presence of other acids or bases in the solution, which can cause a shift in the equilibrium and affect the pH change. Additionally, any errors in measuring the initial pH or concentration of the acid can also impact the accuracy of the calculations.