Ka question

[dennisDDS]

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From my understanding a higher Ka equates to a stronger acid..

Destroyer gives

Ka values
HCN -----------> 6 x 10^-10
CH3COOH ---> 1.8 x 10^-5
HNO2 ----------> 4.5 x 10^-4
C6H5OH -------> 1.3 x 10^-10


Now it says order them in correct order of base strength.
Stonger acid = weaker base right?

so HCN would be the weakest base and which would be the strongest base?

Destroyer says C6H5OH which makes no sense I thought it would be HNO2

any ideas?

 

[Philippines03j]

From my understanding a higher Ka equates to a stronger acid..

Destroyer gives

Ka values
1. HCN -----------> 6 x 10^-10 Pka= 9.3
2. CH3COOH ---> 1.8 x 10^-5 Pka= 4.7
3. HNO2 ----------> 4.5 x 10^-4 Pka= 3.4
4. C6H5OH -------> 1.3 x 10^-10 Pka=9.7 *All estimated Pka=-log(Ka)

Basicity - 4>1>2>3


Now it says order them in correct order of base strength.
Stonger acid = weaker base right?

so HCN would be the weakest base and which would be the strongest base?

Destroyer says C6H5OH which makes no sense I thought it would be HNO2

any ideas?

Ok, We know that we can convert Ka to Pka by taking -log(Ka). Do that for each of them like I did above. We know that the lower the pka the more acidic and the higher the pka the more basic. Hope that makes sense... Let me know if you need more explanation!

Also I found it very helpful if you Know the PKA chart like the back of your hand!

 

[dennisDDS]

thank you so much! I knew how to get pKa but was getting confused in the concept of higher pKa more basic lower pka more acidic..


thanks man..