Q1: When performing titrations, good technique includes: (select all correct ans

Question

Q1: When performing titrations, good technique includes: (select all correct answers).

Q2: When preparing the base solution, we add the base to the water because: (select all correct answers)

Question 1 0 / 1 point When performing titrations, good technique includes: (select all correct answers) En faisant des titrages, il est mieux de: (sélectionnez toutes les réponses correctes) a) performing multiple trials to ensure that the concentration value determined in the trials is accurate to within 2%. faire plusieurs essais pour confirmer que la concentration est déterminée par les essais et precise jusqu'à 296. b) carefully noting the volume of base added. soigneusement noter le volume de base ajouté. c) talking to your partner as the base is being added. parler à votre partenaire pendant l'ajout de la base. d) stirring the solution constantly. brasser la solution constamment.

Explanation / Answer

Ans. #1. Option a. True. Multiple titration trials (at least 3) are done to get a concordant value. The concentration value so obtained at endpoint is accurate to within 2%. Multiple trials minimizes the relative deviation from the exact theoretical value.

# Option b. False. The only thing that matters is the volume to base consumed to reach the endpoint.

There is no need to noting or recording the volume of base added during titration unless specified. Noting the intermediate values would unnecessarily increase the titration time.

# Option c. False. Taking to a friend would deviate your attention and flow of titration process (dropwise addition of base) being conducted by you. It would both increase the experiment time and may cause errors to creep (say, excess base is added) in titration end point value.

# Option d. True. Constant stirring during titration mixes the acid and base molecules uniformly throughout the solution. So, the titration process and endpoint is accurate because it results uniform neutralization reaction simultaneously with accurate tracking the process of titration (say, endpoint is about to reach, endpoint, etc.).

Option e. True. It reduces experiment time simultaneously with leaving the endpoint unaffected.

Option f. False: The color change is reflected within the seconds of addition of base. So, there is no need to waiting for few minutes. Moreover, waiting so long after true endpoint would even cause decolorization of the endpoint solution.

Option g. True. A color change appearing in the solution fades within few second (10-15 seconds or less) because the base takes few second to uniformly disperse in the solution through stirring. If the endpoint is reached, the color would persist for 20-30 seconds or longer. A color change persisting for 20-30 seconds (depending on the laboratory) is taken as endpoint.

Option. h. True. No one knows when the endpoint would be reached. So, the indicator is always added in the beginning to keep a track of the titration from the beginning till endpoint is reached. Moreover, the addition of indicator in beginning also indicates the closeness to the endpoint based on the rate of its decolorization in the solution.

# So, correct options are- a, d, e, g, h

#2. Correct option. e

The solvation of base into water is exothermic, i.e. heat is released during the process.

If all the base is taken in volumetric flask at one time and water is added, the large amount of heat released during the process may cause breakage of the glassware.

To make base (or acid) solution, a small amount of water (around ¼ of flask’s capacity) is first taken in the flask. The flask in then placed on an ice pack of ice-cold water bath. The base is gradually added in small quantity after the previous addition has completely dissolved. It prevents sudden rise in temperature of the flask. Moreover, the final temperature of flask is maintained around the room temperature, only at which the final volume should be made up. Making up the final volume to the mark at too high or too low temperature would cause errors because water, and the solutions have different density at different temperature whereas the flask volume os specified at room temperature.

# Rest of the options are not valid as long as the reason for addition of base into water is sought.

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.