Question

calculate the pH of 0.10 M HCI solution?

Answer 1

first find the concentration of the [OH-] ions in the solution. You do this by using the formula:
[OH]=1x10^-14/[H]

the [h] equals 0.1 bc the M of HCL = the M of H and M of Cl

then you would find the POH. You do this by using the formula: pOH=-log[OH-]

Once you have found the POH you can find pH because PH=14-[pOH]

Answer 2

I don't readily see anything wrong with the answer by anonymous; however, it's a lot of unnecessary work. You don't need to go through the OH or pOH.
pH = -log(H^+)
pH = -log(0.1)
solve.
pH = 1