[ 3 / biz / cgl / ck / diy / fa / ic / jp / lit / sci / vr / vt ] [ index / top / reports ] [ become a patron ] [ status ]
2023-11: Warosu is now out of extended maintenance.

/sci/ - Science & Math

View post   
File: 191 KB, 465x358, 1281848043978.png [View same] [iqdb] [saucenao] [google]
2368026 No.2368026 [Reply] [Original]

Hey /sci/, could you help me out here on something?

How do you determine the mass from the pH? I don't think I'm getting a right answer, and those are the givens:

>mmNaOH = 40g/mol
>M = ?
>V = 1.546L
>pH = 4.34

I'm trying to do it backwards, but I think I'm fucking something up. Any help?

>> No.2368042

NaOH = strong base, you won't finad a solution of it for pH less than 12

>> No.2368049
File: 78 KB, 550x550, 1294126901279.jpg [View same] [iqdb] [saucenao] [google]
2368049

Molar mass tells you nothing about what the pH of a solution will be.
You need to know its pKa or pKb, and how much solute is being put in how much solvent, as well as what other chemicals are being put with it.

>> No.2368058

>>2368026
I think its lookin for molarity bro...capital M is molarity

>> No.2368067

>>2368049
I have the pH of the solution, I need to determine its mass. I figured out to start the equation backwards, but I'm not getting anywhere.

>>2368058
sorry, wrong symbol.

>> No.2368075

Keep in mind what pH is: the negative base 10 log of the hydrogen ion concentration. If you're still having trouble, could you show us your math?

>> No.2368087

From pH you could work out how many molecules of OH(-) there are in solution, from that you can then move on from there.
Remember what pH stands for.
Sure it stands for [H+], but you can work out OH- from that.
Think, once you have a concentration, and a volume...

>> No.2368115

>>2368087
Yeah, what this guy said. Remember that 14-pH=pOH.

>> No.2368140

pOH=(14-pH)=9.66

10^(-9.66)= #

i dont have a calc handy but # is your concentration of OH- in solution and since NaOH is a strong base, the amount of NaOH that is dissolved in solution is equal to the amount you added. So just find total moles of NaOH in solution and multiply by molar mass

>> No.2368158

>>2368140

actually this question doesnt make any sense, pH is too low.

>> No.2368160

>>2368140
Oh yeah totally, assuming complete dissociation. In reality it'd be like 98% or something, but whatever.