Saturday
September 20, 2014

Homework Help: CHEMISTRY HELP!

Posted by Ashley on Monday, July 13, 2009 at 7:49pm.

(1) A beaker with 165 mL of an acetic acid buffer with a pH of 5.00 is sitting on a bench top. The total molarity of the acid and conjugate base in the buffer is 0.100M. A student adds 7.20mL of a 0.320M HCl solution to the beaker. How much will the pH change? The pka of acetic acid is 4.760 . What is the change in pH?

(2) Imagine that you are in chemistry lab and need to make 1.00 L of a solution with a pH of 2.80.
You have in front of you

100mL of 7.0010−2 M ,
100mL of 5.0010−2M , and
plenty of distilled water.

You start to add HCl to a beaker of water when someone asks you a question. When you return to your dilution, you accidentally grab the wrong cylinder and add some NaOH . Once you realize your error, you assess the situation. You have 81.0 mL of HCl and 85.0 mL of NaOH left in their original containers.

Assuming the final solution will be diluted to 1.00 L , how much more HCl (in mL) should you add to achieve the desired pH?

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