April 19, 2015

Homework Help: chemistry

Posted by Sarah (C) on Saturday, April 23, 2011 at 6:10pm.

I have many questions. I have a test tuesday and need to get these problems done and understand them today because i am currently studying. I am in college and my professor has not emailed me back regarding solutions for the review problems she posted. Is it possible if you can help me with these questions.

1) If Ka is small, concentration of w acid (HA) are large. What is a quick way of calculation (H+).
b)(H+)=Ka (Ha)

2) Which of the following salts forms aqueous solutions with pH=7? (How am I suppose to know this from these answers)

a)Na2S b)NaBR c) NaCLO2 d)NaNO2

3)What is the appro pH of solution of NaF?
well the answer is above 7, flouride is a weak base, (but i thought when added with water they neutralize each other forming ions).

4) What is the pH of a 0.15M solution of ammonium bromide? The kb value is 1.8E-5.
(How do i set this up, i tried doing it in place of Ka but that did not work).

5) What is the pH of a 100 ml solution made from 46.2 ml of ).050 M nitric acid and water?

I did stoichometry to try and figure this out and then plug into pH equation but it did not work, what did i do wrong.

6) A buffer system is set up with [HA]=2[A^-]. If Pka is 5.5 what is the pH of the buffer?

7) pH of pure water at 70C knowing pKw=13.16?

I know that at 20C pH=7.

i know these are a lot of questions, but I need the help to set these up and understand what I am doing thank you.

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