PH question need help

Can somebody help me understand this? Thanks

Well you know that:
pH = -log[H+]
and:
[H+] = moles H+ / total volume of solution (dm^3)

We also know that HCl is a strong acid, so that helps a lot in calculating moles of H+ (hint: n=cv)

Brilliant! Thanks a lot for your help One thing: wouldn't water act as an alkali here. Initially, I did HCl + H2O --> H3O+ +Cl- and then things sort of got messed up from there.

We ignore the effect of self ionisation of water.
2H2O <=> H3O+ + OH-

the water doesn't act as an alkali but rather it produces it.

We ignore it as the equilibrium is extremely to the left, hence practically speaking we can assume that there are no hydroxide ions present that could react with the H3O+

We ignore the effect of self ionisation of water.
2H2O <=> H3O+ + OH-

the water doesn't act as an alkali but rather it produces it.

We ignore it as the equilibrium is extremely to the left, hence practically speaking we can assume that there are no hydroxide ions present that could react with the H3O+

I too am stuck on the ionisation of water. I posted a question on *aassumptions, would be great if you could help. **Why did you ignore water in this question too btw?

*There are no assumptions of water.
What is the context of the question?

** Self ionisation of water won't affect pH, just adding the water will dilute acid