We know that pKa is equal to –log(Ka). Thus, pKa of acetic acid is –log(1.8 * 10–5). This is not an easy problem to solve in your head, but there is a trick.

We know that 1 * 10–4 > 1.8 * 10–5 > 1 * 10–5, and we know that –log(1 * 10–4) = 4 and –log(1 * 10–5) = 5. Now we can conclude that our pKa is somewhere between 4 and 5.

Two answer choices fall in this range: 4.2 and 4.7.

1.8 * 10–5 is closer to 1 * 10–5 than it is to 1 * 10–4, so we can pick the answer closer to 5 than to 4 : 4.7.

Recall that pKa is defined as follows:

Here, is the acid dissociation constant. is a measure of the equilibrium strength of an acid and is unique for each acid. The higher the value of , the stronger the acid; however, a particular acid’s value, and subsequently its strength, can never be changed. The only way you can change the of an acid is by changing the identity of the acid itself. This means that the pKa value of an acid is also always constant; therefore, you cannot decrease an acid’s pKa.

Using the definition of pKa, we can see that the pKa of an acid increases as you decrease the acid dissociation constant (). A strong acid will have a high and a low pKa.

The pKa of an acid can never be altered; therefore, changing the concentration of the acid will not alter the pKa of the acid. It might change the amount of hydrogen ions produced and alter the pH; however, the pKa of the acid will stay constant.

We know that pKa is equal to –log(Ka). Thus, pKa of acetic acid is –log(1.8 * 10–5). This is not an easy problem to solve in your head, but there is a trick.

We know that 1 * 10–4 > 1.8 * 10–5 > 1 * 10–5, and we know that –log(1 * 10–4) = 4 and –log(1 * 10–5) = 5. Now we can conclude that our pKa is somewhere between 4 and 5.

Two answer choices fall in this range: 4.2 and 4.7.

1.8 * 10–5 is closer to 1 * 10–5 than it is to 1 * 10–4, so we can pick the answer closer to 5 than to 4 : 4.7.

Recall that pKa is defined as follows:

Here, is the acid dissociation constant. is a measure of the equilibrium strength of an acid and is unique for each acid. The higher the value of , the stronger the acid; however, a particular acid’s value, and subsequently its strength, can never be changed. The only way you can change the of an acid is by changing the identity of the acid itself. This means that the pKa value of an acid is also always constant; therefore, you cannot decrease an acid’s pKa.

Using the definition of pKa, we can see that the pKa of an acid increases as you decrease the acid dissociation constant (). A strong acid will have a high and a low pKa.

The pKa of an acid can never be altered; therefore, changing the concentration of the acid will not alter the pKa of the acid. It might change the amount of hydrogen ions produced and alter the pH; however, the pKa of the acid will stay constant.

First convert concentration of OH- into concentration of H+. Remember that Kw is 1*10-14.

Then, convert concentration of H+ into pH.

Alternatively, you can use the hydroxide concentration to solve for pOH and convert to pH.

First convert concentration of OH- into concentration of H+. Remember that Kw is 1*10-14.

Then, convert concentration of H+ into pH.

Alternatively, you can use the hydroxide concentration to solve for pOH and convert to pH.

The acidity of the solution results from the amount of hydrogen ions present in the solution. We can increase or decrease the pH of the solution by decreasing or increasing the amount of hydrogen ions present, respectively. pKa is a measure of the strength of an acid (meaning how easily it can dissociate into hydrogen ions and its conjugate base). Altering the pH of the solution will have no effect on the strength, and subsequently pKa, of the acid.

This question requires use of the simple titration equation M1V1 = M2V2. The key is to identify that sulfuric acid has two equivalents of acidic hydrogens while NaOH has only one hydroxide equivalent. All wrong answer choices result from making this mistake or other calculation errors.

The acidity of the solution results from the amount of hydrogen ions present in the solution. We can increase or decrease the pH of the solution by decreasing or increasing the amount of hydrogen ions present, respectively. pKa is a measure of the strength of an acid (meaning how easily it can dissociate into hydrogen ions and its conjugate base). Altering the pH of the solution will have no effect on the strength, and subsequently pKa, of the acid.

This question requires use of the simple titration equation M1V1 = M2V2. The key is to identify that sulfuric acid has two equivalents of acidic hydrogens while NaOH has only one hydroxide equivalent. All wrong answer choices result from making this mistake or other calculation errors.