Original post by iamspiderman
1) Find the concentration of hydrogen ions in a solution of 0.01 moldm^-3 of NaOH ?
2) Find the Ph of a solution of 0.020M HCL
2) Find the Ph of a solution of 0.020M HCL
What have you done so far?
..
(edited 7 years ago)
Original post by iamspiderman
For 2)
[h+ ] = 0.020M
Ph = -log 0.020= 1.7
For 1)
Nothing yet I don't know how to work it out
[h+ ] = 0.020M
Ph = -log 0.020= 1.7
For 1)
Nothing yet I don't know how to work it out
Well question 1 isn't asking you to work out the pH so I'm not sure why you're doing that. I'll give you a clue: [H+][OH-]=10^-14.
For question 2, we know the concentration of HCl so what can we say about [H+]?
Original post by sytner9
Concentration fo NaOH is equal to the conc of OH-
It looks to me that you haven't learnt the ionic product of water yet. This is a constant at constant tenperature, Kw=1×10^-14mol^2dm^-6 at 298k. Kw=[OH-][H+]. If you know the concentration of H+ in solution, you can rearrange the Kw formula to find [OH-].
Original post by Protoxylic
It looks to me that you haven't learnt the ionic product of water yet. This is a constant at constant tenperature, Kw=1×10^-14mol^2dm^-6 at 298k. Kw=[OH-][H+]. If you know the concentration of H+ in solution, you can rearrange the Kw formula to find [OH-].
From the first part of the question, it doesn't give you the conc of H+. And yes i have done the ionic product of water. I got an A* at a-level and I am studying chemistry at Oxford.
Original post by Protoxylic
It looks to me that you haven't learnt the ionic product of water yet. This is a constant at constant tenperature, Kw=1×10^-14mol^2dm^-6 at 298k. Kw=[OH-][H+]. If you know the concentration of H+ in solution, you can rearrange the Kw formula to find [OH-].
to be fair you will have to use it but the first step requires the knowledge of what i said
-=
(edited 7 years ago)
-=
(edited 7 years ago)
Original post by sytner9
From the first part of the question, it doesn't give you the conc of H+. And yes i have done the ionic product of water. I got an A* at a-level and I am studying chemistry at Oxford.
It has just occurred to me that I have replied to the wrong person, ignore me.
(edited 9 years ago)
Original post by Chlorophile
Well question 1 isn't asking you to work out the pH so I'm not sure why you're doing that. I'll give you a clue: [H+][OH-]=10^-14.
For question 2, we know the concentration of HCl so what can we say about [H+]?
For question 2, we know the concentration of HCl so what can we say about [H+]?
He got that, he just wrote the 2nd question first followed by 1st.
Original post by iamspiderman
Is this right :
kW= [H+][OH-]
10^-14 = 0.02 x [h+]
[h+] = 10^-14 / 0.02
= 5x10^-3
kW= [H+][OH-]
10^-14 = 0.02 x [h+]
[h+] = 10^-14 / 0.02
= 5x10^-3
Almost! You are getting the concentration of the HO- and H+ mixed up. The question says there are 0.02 moles of NaOH which means there are how many moles of HO- ions? (Hint: NaOH completely dissociates in water as it is a strong base) now that we have the conc. of H+, use the pH formula to work out pH.
Do not look at the spoiler until you are sure you have the answer!
Question 1 I believe you have the correct answer, though I would write 1.70 as 2d.p is generally the accepted form.
Spoiler
.-
(edited 7 years ago)
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