# Physical Chemistry pH question

Borek
Mentor
Well I thought to solve for theta meant to get theta by itself on one side of the equation and have everything else on the other.

So do it.

Didn't I do that with this

θ = ([H+] / Ka) + 1

⇒ θ = ([H+]+[Ka]) / [Ka]

Borek
Mentor
This is definitely wrong, check your math.

Sanity check: if θ=1+x/y and both x and y are positive, θ is larger than 1. By definition θ is lower than 1, so your answer must be wrong.

is "Ka / [H+] = (1-θ) / θ" where I need to start, or is that where I initially messed up.

epenguin
Homework Helper
Gold Member
Better to start again than search for mistake! You are going in circles or backwards in what is a two-line argument. By #8 or again in #18 you had the expression for θ - which is nothing but rewriting the definition of 1b in chemical/mathematical terms. Why go looking for 1/θ or θ/(1-θ) when you are asked for θ? On RHS of the said equation for θ you have one thing twice and another one once. In #1 you have a relation between those two things. Start again and use that relation to eliminate one of them!