Two pH questions i don't understand

[AMan24]

Homework Statement

1) Which solution has the higher pH, a 0.001 M solution of NaOH or a 0.001 M solution of Ba(OH)2?

2) Would a 1.0 × 10^-8M solution of HCl have pH < 7,
pH = 7, or pH > 7? My professor said she shouldn't have put HCl as the solution, but that it doesn't matter apparently.

Homework Equations

The Attempt at a Solution

1) answer is: A 0.001 M solution of Ba(OH)2 has the higher pH

2) answer is: pH < 7

My question:

For 1) How do i determine this? I have no idea how

For 2) I'm doing pH = -log[1.0 x 10^-8] and I am getting pH = 8. How is the answer less than 7?

 

[Bystander]

1.0 × 10-8M solution

Of what?

How do i determine this? I have no idea how

Are you conversant with the concepts of stoichiometry?

 

[AMan24]

Of what?
Are you conversant with the concepts of stoichiometry?

It was HCl but she said it doesn't matter.

Yes i know stoichiometry

 

[Bystander]

Please DO NOT edit. It makes it impossible to follow discussions.

And if the solute were a base? It matters.
What does stoichiometry tell you?

 

[AMan24]

Please DO NOT edit. It makes it impossible to follow discussions.

And if the solute were a base? It matters.
What does stoichiometry tell you?

I guess I could find the number of moles of OH in each of the molecules using molarity. And the Ba(OH)2 would have 2x the number of moles. If that's right then I could also figure it out if it were two different molarities.

 

[epenguin]

Answer to 2 follows directly from definition of pH, and the one you give, I don't know whether it is yours or what you were told, seems wrong to me.

For 1 you are on the right lines; what do you think are the molarities of everything that is there in that Ba(OH)₂ solution?