Question 1

Which of the following best describes the function of litmus paper in a laboratory setting?

Accepted Answer

It qualitatively indicates whether a solution is acidic or basic by changing color.

Question 2

A student tests a solution with blue litmus paper and observes that it turns red. What can be concluded about the solution?

Accepted Answer

The solution is acidic.

Question 3

Which of the following is a limitation of using universal indicator paper compared to a pH meter?

Accepted Answer

Universal indicator paper provides only a rough estimate of pH, not a precise value.

Question 4

A solution has a pH of 3. Which of the following statements is correct?

Accepted Answer

The solution is acidic and has a high concentration of H$$^+$$ ions.

Question 5

Which equation correctly relates pH to the concentration of hydrogen ions in solution?

Accepted Answer

$$\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$$

Question 6

A salt solution is prepared by dissolving sodium carbonate (Na$$_2CO$_3) in $$water. What is the expected pH of the solution and why?

Accepted Answer

The pH will be basic because carbonate ions hydrolyze to produce OH$$^-.$$

Question 7

Which of the following best explains why a solution of ammonium chloride (NH$$_4Cl) in $$water is acidic?

Accepted Answer

NH$$_4^+$$ acts as a weak acid and donates protons to water.

Question 8

A student uses a pH meter to measure the pH of a solution and obtains a value of 12. Which of the following is the best interpretation of this result?

Accepted Answer

The solution is strongly basic.

Question 9

Which of the following pairs of ions would result in a neutral solution when their salt is dissolved in water?

Accepted Answer

Na$$^+$$ and Cl$$^-$$

Question 10

A buffer solution is prepared by mixing acetic acid (CH$$_3$$COOH) and sodium acetate (CH$$_3$$COONa). Which property does this buffer solution exhibit?

Accepted Answer

It resists changes in pH when small amounts of acid or base are added.

Question 11

Which of the following best describes the color change of phenolphthalein in acidic and basic solutions?

Accepted Answer

Colorless in acid, pink in base

Question 12

A solution contains both H$$_2PO$_4^-$$ and HPO$$_4$$^{2-}$$. Which of the following best describes the role of these ions in a biological buffer system?

Accepted Answer

They act as a conjugate acid-base pair to resist changes in pH.

Question 13

A student adds hydrochloric acid (HCl) to a solution of sodium acetate (CH$$_3$$COONa). What is the expected effect on the pH of the solution?

Accepted Answer

The pH will decrease slightly due to the buffer action.

Question 14

Which of the following is the correct net ionic equation for the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH)?

Accepted Answer

$$\mathrm{H}^+ (aq) + \mathrm{OH}^- (aq) \rightarrow \mathrm{H}_2\mathrm{O} (l)$$

Question 15

A solution is prepared by dissolving potassium phosphate (K$$_3PO$_4) in $$water. Which of the following best describes the resulting solution?

Accepted Answer

The solution will be basic due to the hydrolysis of PO$$_4$$^{3-}$$ ions.

Question 16

Which of the following best explains why NaCl is considered a neutral salt?

Accepted Answer

It is formed from a strong acid and a strong base, neither of which hydrolyzes in water.

Question 17

A student is asked to determine the pH of an unknown solution. Which method would provide the most precise measurement?

Accepted Answer

Using a calibrated pH meter

Question 18

A solution of sodium phosphate (Na$$_3PO$_4) is $$mixed with a solution of ammonium chloride (NH$$_4Cl). $$Which of the following ions will act as spectator ions in the resulting mixture?

Accepted Answer

Na$$^+$$ and Cl$$^-$$

Question 19

A patient is diagnosed with metabolic acidosis, a condition where blood pH drops below normal. Which buffer system in the blood helps resist this change in pH?

Accepted Answer

The H$$_2CO$_3/$$HCO$$_3^- ($$carbonic acid/bicarbonate) buffer system

Acids, Bases, and Salts: Laboratory Techniques and pH Measurement

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