GChem help with question

[Toothy2012]

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I feel like I see this question a lot and I have a huge headache so I can't even try to figure it out myself. Can someone please tell me how the pH affects the amount of acid or base you need to add for titrations. For example: What V of HCl is needed if 20ml of 1M NaOH was titrated with 1 M HCl to get pH=2? If anyone can please give me a quick explanation or equation to use I would really appreciate it.

I know its probably really simple, I'm just unbelievably burnt out...any help would be great

Thanks!

 

[souslepont]

nevermind, wrong thread

 

[jigabodo]

I feel like I see this question a lot and I have a huge headache so I can't even try to figure it out myself. Can someone please tell me how the pH affects the amount of acid or base you need to add for titrations. For example: What V of HCl is needed if 20ml of 1M NaOH was titrated with 1 M HCl to get pH=2? If anyone can please give me a quick explanation or equation to use I would really appreciate it.

I know its probably really simple, I'm just unbelievably burnt out...any help would be great

Thanks!

I would break it down to 2 parts.

First, whats the vol. of HCl needed to completely titrat 20ml, 1M NaOH to pH=7 (eq. point)? For this one, know that M1V1=M2V2, so .02L*1=x*1, and you will see that you will need 20ml of HCl to get the NaOH to be neutral, aka pH=7.

Next, you should know the pH=-logH+, so if pH=2, that means in the final concentration there should be .01M of H+ in the solution. With this info in hand, you can then set up the equation using M1V1=M2V2, and then you will get...

.01M(conc. of H) times (.04L+XL)(40ml is after 20+20 from part 1, X is the amount of additional HCL you need to add)=1M (conc. of HCL) times XL (same X as before, the additional HCl you need to add to go from pH=7 to 2)

Then you can solve for X, in liters.

Finally, add the original 20ml you need to get the total Vol. of 1M HCl needed.

 

[Toothy2012]

Thank you so much!😀