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September 1, 2015

Homework Help: chemistry

Posted by unknown on Thursday, March 22, 2007 at 12:15pm.

A titration was performed on 50.0 ml of .250 M NaOH. After the addition of 71.4 ml of HCl,the phenolphthalein indicator changed from pink to colorless. What was the concentration of the HCl? im not sure how to figure this one out but here goes
200*.250*1000=50000
1000*121.4=121400
50000/121400=.412?
that was my best shot

I don't know what you did and since you didn't explain the steps you took OR use any units, I'm clueless.
Here is how you do it.
mols NaOH = mols HCl
M x mL = M x mL
0.250 M x 50 mL = M x 71.4 mL
Solve for M HCl.

Im sorry, that was very stupid of me for not explaining anything. Is this right?
0.250 M x 50 mL= 12.5ml
12.5 M x 71.4ml= 893


no if I solve for m I would have to

0.250 M x 50 mL = M x 71.4 mL
.250M*50=12.5ml
12.5ml=M*71.4
12.5ml=71.4M
12.5/71.4=.175ml

right number, wrong unit.
You are solving for M so M = 0.175M

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