The end point of the acid base/ titration between vinegar and NaOH occurred when:
Question options:
The acid and base neutralized each other.
The phenolphthalein indicator turned faint pink.
The moles of H+ were equal to the moles OH-
All of the above
Frankly I don't know how to answer this question. I don't know if it is a trick question or not. Here is my problem. The equivalence point is the theoretical point at which the acid just neutralizes the base. The end point (different from the equivalence point) is the point in the titration where the indicator turns. We try very hard to make the equivalence point the same as the end point but usually they are not EXACTLY the same but close enough so that the titration error caused by that difference is quite small.
If this is a beginning chemistry class I would answer d. If this is an advanced class I would answer b. I hope this doesn't confuse you but I'll be glad to answer follow up questions on this.
The correct answer is: All of the above.
During a titration between vinegar (acetic acid) and NaOH (sodium hydroxide), the end point is reached when all the acid and base molecules have reacted with each other, resulting in neutralization. At this point, the pH of the solution should be around 7 (neutral).
In addition, a commonly used indicator called phenolphthalein is used in acid-base titrations. When the solution is acidic, phenolphthalein is colorless, but as the base is added and the solution becomes neutral, the phenolphthalein turns faint pink, indicating that the end point has been reached.
Finally, in a neutralization reaction, the moles of H+ from the acid and the moles of OH- from the base should be equal, meaning that all the acid and base have reacted with each other.
Therefore, in the acid-base titration between vinegar and NaOH, the end point occurs when the acid and base neutralize each other, the phenolphthalein indicator turns faint pink, and the moles of H+ are equal to the moles of OH-; hence, all of the given options are correct.
The correct answer is option C: The moles of H+ were equal to the moles OH-.
In an acid-base titration between vinegar (which contains acetic acid, CH3COOH) and sodium hydroxide (NaOH), the reaction can be represented as follows:
CH3COOH + NaOH -> CH3COONa + H2O
During the titration, as the sodium hydroxide solution (the base) is gradually added to the vinegar (the acid), it reacts with the acetic acid, leading to the formation of sodium acetate and water. This reaction is a neutralization reaction, where the acidic and basic components combine to form a salt (sodium acetate, CH3COONa) and water (H2O).
The key point in determining the end point of the titration is when the moles of H+ (hydrogen ions in the acid) become equal to the moles of OH- (hydroxide ions in the base). At this point, complete neutralization has occurred, and all the acid has reacted with the base to form water.
The other options mentioned in the question are also true but not specifically related to the end point of the titration. The first option, "The acid and base neutralized each other," is true but simply describes the overall reaction and neutralization process in a general sense.
The second option, "The phenolphthalein indicator turned faint pink," refers to the use of an indicator in the titration to visually signal the end point. Phenolphthalein is often used as an indicator in acid-base titrations. It is colorless in acidic solutions but turns a faint pink when the solution becomes slightly basic. The phenolphthalein indicator changing color indicates that the solution has reached or is near the end point, but it is not a precise indicator of exactly when the moles of H+ are equal to the moles OH-.
Therefore, option C, "The moles of H+ were equal to the moles OH-," is the most accurate and specific answer to describe the end point of the titration. To determine the end point precisely, it is necessary to calculate the stoichiometry of the reaction and monitor the amounts of the acid and base being added or using an indicator.