5) In a different titration (not the one above), 1.328 g of an unknown monoproti
ID: 908408 • Letter: 5
Question
5) In a different titration (not the one above), 1.328 g of an unknown monoprotic acid required 19.84 mL of 0.106 M sodium hydroxide to reach the equivalence point. What is the molar mass of the acid?
6) Why does the sodium hydroxide solution need to be standardized?
- Sodium hydroxide absorbs and reacts with gases from the atmosphere changing its concentration over time
- You can never trust the prep TA who made the solution, so it is always a good idea to check the concentration
- Readings on a buret in a titration are more accurate than those from a balance, so in general, it is always better to perform a titration than use mass to calculate concentrations
- The sodium hydroxide undergoes decompistion over time so an accurate concentration must be determined every use
7) In a titration of a weak acid with a strong base, why is the equivalent point greater than 7?
Explanation / Answer
5) moles of monoprotic acid = g/molar mass = 1.328/molar mass
It required 0.106 M x 0.01984 L = 2.10 x 10^-3 mols of NaOH
The reacion of monoprotic acid with NaOH is a 1 : 1 ratio basis.
so moles of acid = 2.10 x 10^-3 mols
molar mass of acid = 1.328/2.10 x 10^-3 = 632.381 g
6) Sodium hydroxide solution need to be standardized,
- Sodium hydroxide absorbs and reacts with gases from the atmosphere changing its concentration over time
NaOH is a base, which tends to react with atmospheric CO2 overtime. This reduces the concentration of NaOH from the time it was prepared. Secondly NaOH absorbs moisture from air, and accurate weights are necessary to be known to be used as a primary standard. To get the accurate mass of NaOH for calculations in the experiment we muct standarise the solution.
7) In a titration of a weak acid with a strong base, equivalence point is when all of the acid is converted into its conjugate base that is from HA to A-, so the pH is greater than 7.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.