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chemistry help?? Calculating pH of a weak acid?

0 votes

Example 1:
Calculate the percentage of HF molecules ionized 
in a 0.10 M HF solution. (Ka = 6.8 x 10-4)

*I used the ICE chart, but was not able to know how to apply the 5% rule to this equation. What is the formula for the 5%rule?*

 

 

asked Apr 8, 2015 in CHEMISTRY by heather Apprentice

1 Answer

0 votes

Step 1:

The concentration of the [HF] is 0.100 M.

ka for HF is .

The chemical equation is .

Let us consider change in the concentration:  , then image.

Step 2:

Acid ionization factor .

image

image

Concentration cannot be negative.

image

Step 3:

Percentage ionization :

image

image.

Solution:

image.

answered Apr 8, 2015 by Lucy Mentor
edited Apr 8, 2015 by Lucy

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