a) How would a too low molarity of NaOH affect the calculated molar mass of the unknown acid? b) How would it affect the calculated Ka of the unknown acid?
If mistakenly calibrated pH meter using pH6 buffer instead of pH7 buffer, all ph meter readings were too low.... how does this affect the molar mass of the unknown acid? would this affect the determined pKa of unknown acid?
See your post above.
a) A too low molarity of NaOH would affect the calculated molar mass of the unknown acid in the following way: In an acid-base titration, the molarity of NaOH is used to determine the concentration of the unknown acid. By knowing the volume of NaOH required to neutralize the acid, you can calculate the moles of acid used. Since the molar mass is calculated by dividing the mass of the unknown acid by the moles, a lower molarity of NaOH would result in an overestimation of the moles of acid. This would lead to an underestimated molar mass of the unknown acid.
b) The calculated Ka of the unknown acid would not be affected by a too low molarity of NaOH. The Ka value is determined by the equilibrium constants of the acid dissociation reaction. The molarity of NaOH is used to find the moles of acid reacted and to calculate the concentration of the acid, but it does not directly impact the Ka value.
Regarding your second question, if you mistakenly calibrated the pH meter using a pH6 buffer instead of the pH7 buffer, all pH meter readings would be shifted downwards. This would affect the determination of the molar mass of the unknown acid because the pH meter readings are used to determine the equivalence point in the titration. The equivalence point is where the moles of NaOH added to the reaction are stoichiometrically equal to the moles of the acid. If the pH meter readings are lower than expected, it would incorrectly indicate that less NaOH has been added, leading to an underestimation of the moles of acid and consequently the molar mass.
Similarly, the determined pKa of the unknown acid would be affected by the mistakenly calibrated pH meter. The pKa value is determined from the pH at the half-equivalence point, which is where the concentration of the acid and its conjugate base are equal. If the pH meter readings are too low, it would incorrectly indicate a lower pH at the half-equivalence point, leading to an inaccurate determination of the pKa value.