# Chem: Calculate volume given molarity and pH

• Winning
In summary, to calculate the volume of a solution given the molarity and pH, you can use the formula V = n/M, where n is the number of moles and M is the molarity. The number of moles can be found using the formula n = MV, and the pH is used to determine the concentration of hydrogen ions in the solution. Molarity and pH are inversely related, meaning that as molarity increases, pH decreases. It is important to use consistent units of moles per liter and liters when using this calculation. This calculation can only be used for solutions with a single solute and assumes the solution is dilute. The accuracy of this calculation depends on the accuracy of the molarity and pH values used
Winning

## Homework Statement

What volume of solution is needed to dissolve 1.0 mol of a strong base such as KOH to make a solution whose pH is 12.5?

## Homework Equations

$$KOH_{(s)} \rightarrow K^{+}_{(aq)} + OH^{-}_{(aq)}$$

$$pH = -log[H_{3}O^{+}]$$

## The Attempt at a Solution

I'm not going to bother with the pretty print here... sorry

12.5 = -log[H3O+]
[H3O+] = 10^-12.5
[H3O+] = 3.2 x 10^-13 mol/L

[OH-] = 10^-14/(3.2 x 10^-13) M
[OH-] = 3.1 x 10^-2 M

1.0 mol * 1 L / (3.1 x 10^-2) mol = 32 L

ans: 32 L

I feel like I'm wrong... help please.

Last edited:
Winning said:
I feel like I'm wrong...

You feel wrong.

## 1. How do I calculate the volume given the molarity and pH?

To calculate the volume, you will need to use the formula V = n/M, where n is the number of moles and M is the molarity. You can find the number of moles by using the formula n = MV, where M is the molarity and V is the volume in liters. To calculate the volume, you will also need to use the pH to determine the concentration of hydrogen ions (H+) in the solution.

## 2. What is the relationship between molarity and pH?

Molarity and pH are inversely related. This means that as the molarity increases, the pH decreases, and vice versa. This is because pH is a measure of the concentration of hydrogen ions (H+) in a solution, and molarity is a measure of the concentration of a solute in a solution. As the concentration of the solute increases, the concentration of hydrogen ions decreases, resulting in a lower pH.

## 3. Can I use any units for molarity and volume in this calculation?

No, it is important to use consistent units for molarity and volume in this calculation. Molarity is typically expressed in moles per liter (mol/L), and volume is typically expressed in liters (L). If you use different units, you will need to convert them to the appropriate units before performing the calculation.

## 4. Can I use this calculation for all types of solutions?

This calculation can be used for solutions that contain only one solute. If the solution contains multiple solutes, you will need to use a different formula to calculate the volume. Additionally, this calculation assumes that the solution is dilute, meaning that the volume of the solute is negligible compared to the volume of the entire solution.

## 5. How accurate is this calculation?

The accuracy of this calculation depends on the accuracy of the molarity and pH values used. If these values are measured accurately, the calculation should be accurate. However, there may be some experimental errors or uncertainties that could affect the accuracy of the result.

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