pH solution preparation

[Cin]

I have been given 2 methods to make up pH solutions which are both different. Are these right or not??

Method 1:pH 2 (1ml of 1M HCl in 99mls water)
pH 4 (1ml of pH2 soln in 99mls water)
pH 6 (1ml of pH4 soln in 99mls water)

Method 2: pH 2 (1ml of 0.1M HCl in 10ml water)
pH 3 (1ml of pH 2 in 10ml water)
pH 4 (1ml of pH3 in 10ml water)

[smiley]

Well, if you do the math, you've got exactly the same thing.

When you dilute 1M HCl 1mL in 100mL, then you get 0.01M
When you dilute 0.1M HCl 1mL in 10mL, then you get 0.01M

So its same/same either way.

Just remember, if you add 1mL to 99mL (which is 1 in 100) then you move the decimal point 2 places - i.e. 1M to 0.01M, 0.01 to 0.0001M etc. When you add 1mL to 9mL (1 in 10) then you move the decimal point by 1, i.e. 0.1M to 0.01M, etc.

[Ocker]

That's alright if you want HCl of pH 2 but the moment it comes in contact with a test tube it's contaminated and changes, what I think you want is a Buffer solution that takes a fair amount of contamination before it changes search for pH Buffer