/sci/ - Science & Math » Thread #12074577

966KiB, 500x660, 99e.gif

View Same Google iqdb SauceNAO

Amount of acid to change water ph

Anonymous Tue 01 Sep 20:39:47 2020 No.12074577 View Reply Original Report

Quoted By: >>12074645 >>12074905 >>12076282

I need to change the ph of a solution for hydroponics
Let's say I have a 20L water/nutrients solution with pH = 7 and I want to lower it to 5.5, and I have a bottle of 30% H2SO4, how much acid do I need to add?
I don't need extreme precision, my target pH is between 5.5 and 6.5

Anonymous

Anonymous Tue 01 Sep 2020 20:56:35 No.12074645 Report

Quoted By:

>>12074577
sorry, i have absolutely no idea how to help but can't you just add small amounts of h2so4, test pH, rinse and repeat till desired pH?

Anonymous

Anonymous Tue 01 Sep 2020 22:17:25 No.12074905 Report

Quoted By:

>>12074577
Lool up a ph calculator online, plenty of them around

Anonymous

Anonymous Wed 02 Sep 2020 09:12:45 No.12076282 Report

Quoted By: >>12076329

>>12074577
pH = -log[H+]
[H+] = 10^(-pH)
in pH 7 solution, there are 10^(-7) moles per litre of H+ ions
in pH 5.5 solution, there are 10^(-5.5) moles per litre of H+ ions
you need to add 10^(-7) - 10^(-5.5) = 3.0623 * 10^(-6) mol/L * 20 L = 6.1246 * 10^(-5) moles of H+ ions to the water/nutrients solution
1 mole of H2SO4 will produce 2 moles of H+ ions (because it's a diprotic, strong acid), so you need to add 6.1246 * 10^(-5) / 2 = 3.0623 * 10^(-5) moles of H2SO4 to the solution
30% H2SO4 means that the solution contains 30 g of H2SO4 molecules for every 100 g of solution, and by n = m/M (moles = mass / molar mass), m = nM = 3.0623 * 10^(-5) * (2*1.008+32.06+4*15.999) = 3.0032 * 10^(-3) g of H2SO4 * 100/30 = 1.0011 * 10^(-2) L of 30% H2SO4 is needed

To reduce the pH of your 20 L water/nutrients solution from 7 to 5.5, you need about 10 mL of 30% H2SO4

Anonymous

Anonymous Wed 02 Sep 2020 09:39:30 No.12076329 Report

Quoted By:

>>12076282
To calculate how much H2SO4 to reduce the pH to 6.5 is left as an exercise to the OP.

Capcode	All Only User Posts Only Moderator Posts Only Admin Posts Only Developer Posts
Show Posts	All Only With Images Only Without Images
Deleted Posts	All Only Deleted Posts Only Non-Deleted Posts
Ghost Posts	All Only Ghost Posts Only Non-Ghost Posts
Post Type	All Only Sticky Threads Only Opening Posts Only Reply Posts
Results	All Grouped By Threads
Order	Latest Posts First Oldest Posts First

Your latest searches