Which of the four solutions (all same concetrations, same volume) requires:
a) the greatest amount of base for complete titration?
b) the greatest amount of base to titrate to any given pH?
HCl, acetic acid, formic acid, HNO3.
i put HCl for both... is that correct?
To determine which of the four solutions requires the greatest amount of base for complete titration and to titrate to any given pH, you need to consider the properties of each acid.
a) For complete titration, the acid that requires the greatest amount of base is the one with the highest molar mass, assuming all solutions have the same concentration and volume. This is because a higher molar mass corresponds to a greater number of moles, which, in turn, requires a larger amount of base to neutralize.
The molar masses of the given acids are:
- HCl: 36.46 g/mol
- Acetic acid (CH3COOH): 60.05 g/mol
- Formic acid (HCOOH): 46.03 g/mol
- HNO3: 63.01 g/mol
Therefore, HNO3 has the highest molar mass and requires the greatest amount of base for complete titration.
b) To determine which acid requires the greatest amount of base to titrate to any given pH, it is important to consider the acid dissociation constant (Ka) for each acid. The acid with a smaller Ka value will require a greater amount of base to reach a given pH.
The Ka values of the given acids are:
- HCl: Strong acid, fully dissociates in water (Ka is essentially infinity)
- Acetic acid (CH3COOH): Ka = 1.8 x 10^(-5)
- Formic acid (HCOOH): Ka = 1.8 x 10^(-4)
- HNO3: Strong acid, fully dissociates in water (Ka is essentially infinity)
Since HCl and HNO3 are both strong acids that fully dissociate in water, their Ka values are very large or effectively infinity. Acetic acid and formic acid, on the other hand, have smaller Ka values. This indicates that they do not dissociate as completely and will require a larger amount of base to achieve a given pH.
Therefore, HCl is the correct answer for both a) and b) since it has the highest molar mass and is a strong acid, requiring the greatest amount of base for complete titration and to titrate to any given pH.