Unit 2 Acids and Bases Questions

[kat148]

Hi guys, I'm having trouble with some questions and was hoping for some assistance:

Q) Gastric juice consists essentially of a solution of hydrochloric acid and the enzyme pepsin. It is normally at a pH in the range of 0.3 to 1.2 with the lower figure leading to hyperacidity. The commonly available antacids provide relief from hyperacidity. Aluminium hydroxide is sometimes used for this purpose.

What mass of aluminium hydroxide must be used in an antacid tablet if it is designed to increase the pH of 500 ml of gastric juice from 0.3 to 0.12?

..now would the first step be to calculate the in 500ml of hydrochloric acid :S ?


Thanks in advance!

[chem-nerd]

to increase pH from 0.3 to 1.2 (in 500mL):

n(H₃O⁺) to be neutralised = (10^-0.3 - 10^-1.2)/2 = 0.219 mol

n(Al(OH)₃) = 1/3 x 0.219 mol

the use m = n x Mr

[kat148]

oh I see it now. Thanks for your help chem-nerd!

[kat148]

Stuck on this question..

A commonly used primary standard acid in analytical chemistry is potassium hydrogen phthalate () - a monoprotic acid of molar mass
In a titration exercise it is found that a sample of 1.305g of potassium hydrogen pthalate requires 17.28 ml of sodium hydroxide solution to neutralise it.

What is the molarity of the NaOH solution.

Can anybody lead me in the right direction? Thanks

[Edmund]

First find the number of moles of potassium hydrogen phthalate.

n(potassium hydrogen phthalate) = n(NaOH)

Now we have n(NaOH), V(NaOH), we can calculate C.

[kat148]

Thanks Edmund!

[kat148]

Stoic question:

What volume of 0.100M is required to react with 15 mL of 0.050M ?

Again, how would I apporach this?

Thanks for any advice