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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Buddy_123 on February 12, 2021, 08:09:03 PM

Title: Finding the pH of NaCl dissolved in water
Post by: Buddy_123 on February 12, 2021, 08:09:03 PM
Is there a way to use the ice table to find the pH of 0.1 NaCl?

I know that the strong acid (HCl) and strong base (NaOH) means that it is neutral so the pH is 7. But I'm not sure how I'd show that using the Ice table.
Title: Re: Finding the pH of NaCl dissolved in water
Post by: jeffmoonchop on February 12, 2021, 10:47:02 PM
The pH of a salt solution is low, 5
Title: Re: Finding the pH of NaCl dissolved in water
Post by: AWK on February 13, 2021, 01:41:51 AM
The pH correction related to the ionic strength of the solution is outside the ICE table. For a 0.1 M NaCl solution, this correction will be negligible. Read an advanced physical chemistry textbook.
Title: Re: Finding the pH of NaCl dissolved in water
Post by: AWK on February 13, 2021, 03:03:11 AM
The pH of a salt solution is low, 5
Show your calculations.
Title: Re: Finding the pH of NaCl dissolved in water
Post by: jeffmoonchop on February 16, 2021, 11:57:19 AM
The pH of a salt solution is low, 5
Show your calculations.

Dissolve salt in water, measure pH.
Title: Re: Finding the pH of NaCl dissolved in water
Post by: DrCMS on February 17, 2021, 08:38:54 AM
The pH of a salt solution is low, 5
Show your calculations.

Dissolve salt in water, measure pH.

Did that just now and I got pH ~6.5
Title: Re: Finding the pH of NaCl dissolved in water
Post by: shchavel on February 25, 2021, 09:58:13 AM
The pH of a salt solution is low, 5
Show your calculations.

Dissolve salt in water, measure pH.

Did that just now and I got pH ~6.5

Because it depends on water more than on salt)
Title: Re: Finding the pH of NaCl dissolved in water
Post by: DrCMS on February 25, 2021, 11:36:52 AM
The pH of a salt solution is low, 5
Show your calculations.

Dissolve salt in water, measure pH.

Did that just now and I got pH ~6.5

Because it depends on water more than on salt)

The water I used was distilled and had a measured pH, on a recently calibrated pH meter, of ~7.1 before I added the salt and ~6.5 afterwards.
Title: Re: Finding the pH of NaCl dissolved in water
Post by: jeffmoonchop on February 25, 2021, 11:58:23 AM
Maybe I was exaggerating a little when I said 5, but on the whole salt reduces pH. Could be to do with additional absorption of CO2 from the atmosphere. The saline solution we use measures 5.5. How much salt did you add?
Title: Re: Finding the pH of NaCl dissolved in water
Post by: DrCMS on February 25, 2021, 12:09:06 PM
How much salt did you add?

Enough to make 0.1M NaCl
Title: Re: Finding the pH of NaCl dissolved in water
Post by: Vidya on March 01, 2021, 01:27:03 AM
May be due to some impurity in the salt.
Title: Re: Finding the pH of NaCl dissolved in water
Post by: DrCMS on March 01, 2021, 11:49:27 AM
May be due to some impurity in the salt.

It was >99% NaCl sold by a reputable chemical lab supplier.