[Neil_AUS]

Hey there,

I'm an Australian student, I'm calling all the chemistry gurus to help me out. (I'm in high school here).

So basically, we need a bit of chem to do this practical in bio, which we're getting assessed on.

I need 5 test tubes with pHs: 3, 5, 7, 10.

So test tube 7 = distilled water.

My method needs to be something like add 1 drop of X into test tube 1, check pH, keep adding drop until its pH is 3.

Repeat for test tube 2 and 4 to get their pH to 5 and 10 respectively.

Anyone know these 2 solutions? To increase the pH and decrease it?

Please give me 2 simple solutions, cheers. I'm just a student studying bio in Aust, and I have no clue about chemistry. Just need help so I don't fail tomorrow.

Thanks,

Neil

[Borek]

Anyone know these 2 solutions? To increase the pH and decrease it?

Adding acid always lowers pH, adding base always make it higher.

But - as the pH scale is logarithmic - it is not an easy task to change the pH to a given value just by adding acid/base, especially when the pH values are quite distant, as in your case.

Please give me 2 simple solutions, cheers. I'm just a student studying bio in Aust, and I have no clue about chemistry.

I am afraid it won't work this way. While preparing these solutions is not very complicated, the best approach calls for use of buffer solutions, and that in turn requires a bit of knowledge and understanding of the underlying chemistry.

[XeLa.]

Yeah, like Borak said, preparation of acids/bases of the like you're after does require a bit of extra knowledge. See if you can look up information on things such as pKa or the Henderson-Hasselbalch equation, or ask your school's chemistry teacher how you would make a buffered solution with a certain pH.

I hope this helps,
KungKemi