College Chemistry : pH

Study concepts, example questions & explanations for College Chemistry

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Example Questions

Example Question #1 : P H

Determine the pH of a solution that is .

Possible Answers:

Correct answer:

Explanation:

Since  is a strong acid, the concentration of  is equal to the concentration of the acid itself.

Thus, .

Recall how to find the pH of a solution:

Plug in the given hydronium ion concentration to find the pH of the given solution.

Remember to maintain the correct number of significant figures.

Example Question #2 : P H

Find the pH for a solution that is   by mass. Assume a density of  for the solution.

Possible Answers:

Correct answer:

Explanation:

Start by assuming that there is  liter of the solution. From this, we can use the given density to find the mass of the solution.

Next, find the mass of  that is present in the solution.

Now, find the number of moles of  that is present in the solution.

Since we initially assumed that we had  liter of the solution, we now also know the concentration of  in this solution.

Since  is a strong acid, the concentration of hydronium ions in the solution will be the same as the concentration of .

Recall how to find the pH of a solution.

Example Question #2 : P H

Find the pH of a solution that is  by mass. Assume a density of  for the solution.

Possible Answers:

Correct answer:

Explanation:

Start by assuming that there is  liter of the solution. From this, we can use the given density to find the mass of the solution.

Next, find the mass of  that is present in the solution.

Now, find the number of moles of  that is present in the solution.

Since we initially assumed that we had  liter of the solution, we now also know the concentration of  in this solution.

Since  is a strong acid, the concentration of hydronium ions in the solution will be the same as the concentration of .

Recall how to find the pH of a solution.

Example Question #3 : P H

Which of the following techniques will decrease the pH of a solution? 

Possible Answers:

Increasing the amount of solvent

Decreasing the concentration of protons

Increasing the amount of Hydroxide molecules

Increasing the concentration of protons 

Adding more acid at the same Molarity of the solution

Correct answer:

Increasing the concentration of protons 

Explanation:

Increasing the concentration of protons of a solution will make the solution more acidic; therefore, it lowers the solution’s pH. Decreasing the concentration of protons will make the solution more basic, raising the pH. Adding more acid of the same molarity of the original solution will not increase the concentration of protons and will not increase acidity or lower the pH. Increasing the amount of hydroxide ions will make the solution more basic and raise the pH. Increasing the amount of solvent will lower the concentration, affecting molarity and not lowering the pH. 

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