Final answer:
D. 1.25 M KOH,The correct titrant to use for titration of lactic acid is as it is a strong base that will react with the monoprotic acid to determine its concentration.
Step-by-step explanation:
To determine the exact concentration of a sample of lactic acid through titration, you should use a strong base as the titrant. The correct option from the provided choices would be D. 1.25 M KOH, which stands for potassium hydroxide.
Potassium hydroxide is a strong base and will react completely with the monoprotic lactic acid to produce water and a salt. The other options are either acids, which cannot act as a titrant in an acid-base titration, or not related to titration (ethanol).
By adding a known concentration of KOH to the lactic acid sample and measuring how much is required to reach the equivalence point, the concentration of lactic acid can be calculated.
Since lactic acid is a monoprotic acid, we need a monoprotic base as the titrant. A monoprotic base is one that donates only one proton (H+ ion) per molecule.
Based on the options provided, the correct titrant to use for the titration is B. 10.5 M NaOH (sodium hydroxide). Sodium hydroxide is a strong base and will react completely with the lactic acid, allowing us to determine the exact concentration of the lactic acid sample.