11. What mass of sodium benzoate should be added to 160.0mL of a 0.17M benzoic acid solution in order to obtain a buffer with a pH of 4.30?

I don't think we have any experts in the school subject of NCCU.

millimols benzoic acid = mL x M = about 27 but that's an estimate and you should redo the math.

Then pH = pKa + log (base)/(acid)
4.30 = pKa benzoic acid + log benzoate/27
Look up the value of pKa for benzoic acid, substitute, solve for base. That will be millimols sodium benzoate needed. Change to mols, then mols = g/molar mass. You know molar mass and mols, solve for grams.

I would have answered this much quicker if you had typed in the subject instead of something obscure like NCCU.

To answer this question, we need to understand the concept of a buffer solution and how to calculate the mass of a compound required to create the desired buffer solution.

A buffer solution is a solution that resists changes in pH when an acid or a base is added to it. It consists of a weak acid and its conjugate base (or a weak base and its conjugate acid). In this case, we are trying to create a buffer using benzoic acid (C6H5COOH) and its conjugate base, sodium benzoate (C6H5COONa).

The Henderson-Hasselbalch equation is commonly used to calculate the pH of a buffer solution:

pH = pKa + log([A-]/[HA])

Where:
- pH is the desired pH of the buffer solution,
- pKa is the dissociation constant of the acid (benzoic acid in this case),
- [A-] is the concentration of the conjugate base (sodium benzoate),
- [HA] is the concentration of the weak acid (benzoic acid).

Given that the desired pH is 4.30, we know the pH and pKa values. The pKa for benzoic acid is 4.20 (this value needs to be known from a reference source, such as a textbook or database).

Now, let's find the concentrations of benzoic acid and sodium benzoate in 160.0 mL of the 0.17M benzoic acid solution.

Concentration (mol/L) = moles/volume (L)

Concentration of benzoic acid ([HA]):
[HA] = 0.17 M

Concentration of sodium benzoate ([A-]):
[A-] = 0

Since we don't have any sodium benzoate initially, we need to calculate the amount (in moles) of sodium benzoate required to react with the benzoic acid to create the buffer:

moles of [A-] = moles of [HA]

Assuming we have x moles of sodium benzoate:
x moles = 0.17 M x (160.0 mL / 1000)

Once we have the moles, we can calculate the mass of sodium benzoate:

mass = moles x molar mass

The molar mass of sodium benzoate (C6H5COONa) can be calculated by adding the atomic masses of each element:
molar mass = (C atomic mass) + 6(H atomic mass) + (C atomic mass) + (O atomic mass) + (O atomic mass) + (Na atomic mass)

After calculating the mass, you will have the answer to the question: What mass of sodium benzoate should be added to 160.0 mL of a 0.17M benzoic acid solution in order to obtain a buffer with a pH of 4.30.