[kenny1999]

For most of the Chemistry textbook , usually in the introduction part of acid and base, they like to use a chart showing the approx. pH values of some common substances.

Like HCl = 1.0, Vinegar = 2.0 , Softdrink = 3.0, Lemon = 3.5, Tea = 5.0 , Milk = 6.8 etc..

However, for 0.1M HCl, it is true that pH=1. But if the HCl is 0.2M, then the pH of it is 2
, pH is affected by the concentration of the substance, so what is the meaning of the book saying that it's pH is 1.0 while it is affected by the concentration at different situations. pH of a concentrated weak acid may be higher than the pH of a dilute strong acid.

Please help. Thanks.

[enahs]

Just a poorly worded books. You are totally correct.

[DevaDevil]

However, for 0.1M HCl, it is true that pH=1. But if the HCl is 0.2M, then the pH of it is 2

sorry, it isn't pH of 0.2 M HCl soln = 0.7

pH is affected by the concentration of the substance, so what is the meaning of the book saying that it's pH is 1.0 while it is affected by the concentration at different situations. pH of a concentrated weak acid may be higher than the pH of a dilute strong acid.

you are absolutely correct there

[rajajidwivedi]

pH of 0.2M HCl solution is 1-log2 means it is approx 0.69 and one more thing that i would like to share that pH can not be less than zero does not matter that how concentrate the acid is. for eg pH of 2 M HCl solution will be zero not -2.

[Borek]

one more thing that i would like to share that pH can not be less than zero does not matter that how concentrate the acid is. for eg pH of 2 M HCl solution will be zero not -2.

You are wrong, pH is NOT restricted to positive values, just like it is not restricted to values below 14.