Some Questions

[ChemSiddiqui]

Hi, I have some questions please answer them for me:

 

which is true about catalyst;

 

A. They lower the activation energy for a reaction

 

OR

B. They provide a different pathway, one with lower activation energy.

 

Now some books say the former but my teacher believes the latter is actually true. What is your say on it.

 

The below is a worked example from a book which I think has mistakenly printed it. what you say:

 

 

"

What is the pH of 2 mol dm-3 NaOH?

 

NaOh is a strong base, so it exists as ions.

 

So [OH] = [NaOH] = 2 mol dm-3

 

so -log[OH] = -log2

 

so pOH = - 0.3

 

so pH = 14 - (-0.3) = 14.3 "

 

Now how can the pH of anything be 14.3.

 

please help out in the above situations. thnx

[Darkblade48]

For the first question, my interpretation is that a) is correct; as that is what I was taught. I can see how b) could be interpreted as correct, however.

 

For the second question, it is very possible for pH to be either greater than 14, or less than 0. For example, a 10 molar solution of HCl would generate a pH of -1 (HCl, a strong acid, assume complete dissociation of H+ and Cl-, you get 1 molar of protons, -log(10) (base 10) gives you -1).