Thursday

March 26, 2015

March 26, 2015

Posted by **Jenni** on Wednesday, December 15, 2010 at 4:58pm.

- Chemistry!! -
**DrBob222**, Wednesday, December 15, 2010 at 5:47pm...........HCN + H2O ---> H3O^+ + CN^-

initial....0.100...........0.......0

change.....-x..............+x......+x

final...0.100-x.............x.......x

Ka = (H3O^+)(CN^-)/(HCN)

Now substitute into Ka expression the values from the ICE chart.

Ka for HCN is 7.2E-4 from an old book of mine but you need to use the value found in your text/notes.

7.2E-4 = (x)(x)/(0.1-x)

Solve for x = (H3O^+) and convert to pH.

(CN^-) is the same.

NOTE: If you solve the EXACT equation I have written above you must solve a quadratic equation. Most calculators do that with no problem.

Post your work if you get stuck.

- Chemistry!! -
**Lisa**, Wednesday, December 15, 2010 at 6:24pmSo is Ka water H2o? not sure where you got 7.20 in my chart 7.2 goes with H2PO4^-

there is nothing for (H3O+) but I got 4.69 for CN- and 9.31 for HCN

I am so lost...

- Chemistry!! -
**DrBob222**, Wednesday, December 15, 2010 at 6:41pmIf you re-read my post I told you where I obtained 7.2E-4. Since you didn't include it in your post I had to look in one of my old texts BUT I told you to look in your text and use the value you found there.

What do you mean there is nothing for H3O^+. That's what you are calculating. And HCN can't possibly be 9.31. It was 0.100 in the problem.

**Answer this Question**

**Related Questions**

math - round result to two decimal places...the answer i have is: 7.023 so two ...

Sequences - Show full steps: 1a) Determine the formula for the nth term for 7,12...

Chemistry - Estimate the equilibrium constant for the weak acid HCN, if a 4.68×...

Chemistry 30 - 50.0 mL of 0.200 M NaOH neutralized 20.0 mL of sulfuric acid. ...

Chemistry - 1. Calculate the pH of a buffer solution that contains 0.32 M ...

Chemistry - 1. Calculate the pH of a buffer solution that contains 0.32 M ...

math - average of rainfall reno-0.19mm sahara-0.17mm mojave 0.1mm tempe-0.24 ...

Chemistry! - Determine the pH of the following, giving your answers to two ...

chemistry - What is the percent ionization of a 1.38 mol/L weak acid if its Ka...

Pre Cal - Two forces with magnitudes of 100 and 50 pounds act on an object at ...