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# A2 acids and bases watch

1. Its (iv) i dont get but the other parts are needed

A sample of hydrochloric acid contains 7.05 × 10–3 mol of hydrogen chloride in
50 cm3 of solution.
(i) Calculate the concentration, in mol dm–3, of this hydrochloric acid.

(ii) Write an expression for the term pH.

(iii) Calculate the pH of this hydrochloric acid.

(iv) When water is added to this 50 cm3 sample of acid the pH increases. Calculate
the total volume of the solution when the pH becomes exactly 1.00

i know that pH=1 which would mean [H+]= 0.1 but what do you do with that :/
2. For iv you need to find the volume of the solution where the concentration is 0.1 moldm-3. You know concentration is related to volume by moles, in the equation n = c * v.

So, if you know your required concentration, and you're looking for the volume, then the equation rearranges to: v = n/c

which with this would be: V = n / 0.1.

So now, calculate the number of moles you've got, and add it to that formula to get the volume, which will be in dm3, then, if necessary convert to cm3 by times by 1000.
3. (Original post by Stiff Little Fingers)
For iv you need to find the volume of the solution where the concentration is 0.1 moldm-3. You know concentration is related to volume by moles, in the equation n = c * v.

So, if you know your required concentration, and you're looking for the volume, then the equation rearranges to: v = n/c

which with this would be: V = n / 0.1.

So now, calculate the number of moles you've got, and add it to that formula to get the volume, which will be in dm3, then, if necessary convert to cm3 by times by 1000.
Oh yes thanks!

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