Chemistry help pH

For the first one, it's a weak acid so it has a slightly higher pH. When you use a lower concentration of the weak acid, the concentration of H+ decreases and therefore the pH increases (pH = -log[H+]).
For the second one, you are using H2SO4 which is a strong acid, so fully dissociates in water, and it's also diprotic so has 2H+ for each molecule (so if there was 1 mol dm^-3 of H2SO4, there would be 2 mol dm^-3 of H+). This means that the concentration of H+ is much higher and therefore the pH is much lower.
I hope this helps

Ahh that makes sense got you thanks a lot!!

One for quick question if you don’t mind-

Question- state the role of c.
Answer - catalyst- appears in rate equation but not stoichiometric equation

I thought role of c is an intermediate?
What’s the difference between an intermediate and a Catalyst is this scenario and how can you distinguish between the two?

Thanks for your time!!

Np, I'm happy to help
An intermediate is a molecule produced by the reactants reacting which then undergoes further reaction to form the actual product seen in the equation. In this case, an intermediate would be a molecule formed when A and B react which then reacts again to form D. C can't be a catalyst because the question states that A reacts with B in the presence of C. Since C is already there when the reaction starts, it means that it wasn't formed by A and B reacting. You can tell that C is a catalyst because changing the concentration of C affects the rate of reaction but it's not a reactant. (Also, usually when you say there's a catalyst in a reaction you use the wording "in the presence of X catalyst.").
I hope that makes sense

Ahhhh that makes so much more sense thank you! It cleared a lot up