Equal volumes of two monoprotic acid solutions (A and B) are titrated with identical NaOH solutions. The volume needed to reach the equivalence point for solution A is twice the volume required to reach the equivalence point for solution B, and the pH at the equivalence point of solution A is higher than the pH at the equivalence point for solution B. Which statement is true? a. The acid in solution A is more concentrated than in solution B and is also a stronger acid than that in solution B. b. The acid in solution A is less concentrated than in solution B and is also a weaker acid than that in solution B. c. The acid in solution A is more concentrated than in solution B and is also a weaker acid than that in solution B. d. The acid in solution A is less concentrated than in solution B and is also a stronger acid than that in solution B.

Understanding the equivalence point is crucial when performing an acid-base titration. It is the juncture in the titration process where the amount of the titrant (usually a base) added is just enough to completely neutralize the acid in the solution. At this specific point, the moles of acid are equal to the moles of base, and ideally, all the acid has been converted to water and a salt. Knowing the equivalence point is vital because it indicates that the titration is complete and allows for the calculation of the original acid concentration if the base concentration is known.

In the case of the exercise, it was observed that it takes twice the volume of NaOH to reach the equivalence point for solution A compared to solution B. This is a clear indication that solution A either has a higher concentration of acid or a different acid strength, which directly influences the amount of titrant needed to achieve neutrality.

Acid concentration refers to the amount of acid present in a solution, usually expressed in molarity (moles of acid per liter of solution). When comparing two acids with equal volumes and the same base used for titration, the volume of base required to reach the equivalence point can provide insights into the relative acid concentrations. If one solution requires more titrant, it usually signals a lower concentration of acid, since each mole of base is neutralizing fewer moles of acid, hence more volume is needed to reach the equivalence point.

In our exercise, since solution A needs twice the volume of NaOH compared to solution B, this implies that the concentration of acid in solution A is lower. If solution A had a higher concentration of acid, it would require less NaOH to neutralize the same amount of acid.

Acid strength describes how well an acid donates protons (hydrogen ions) when in an aqueous solution. Strong acids completely dissociate in water, releasing a larger number of protons and resulting in a lower pH. In contrast, weak acids dissociate to a lesser extent, resulting in a higher pH due to fewer available protons.

In the exercise, the higher pH at the equivalence point for solution A indicates that it contains a weaker acid than solution B. A strong acid would release more protons, producing a solution with a lower pH upon neutralization. Hence, a higher pH signifies that the acid is not donating as many protons, qualifying it as a weaker acid.

The pH level is a measure of the acidity or basicity of a solution, on a scale from 0 to 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic. During titration, the pH changes as an acid reacts with a base, and monitoring the pH is integral for determining the equivalence point.

The pH at the equivalence point also helps in identifying the strength of the titrated acid. Strong acids result in an equivalence point pH that is on the acidic side (less than 7). For weak acids, the equivalence point pH is higher, often above 7, because the conjugate base of the weak acid affects the pH of the solution. In our example, a higher equivalence point pH for solution A suggests it is a weaker acid compared to solution B.