How to calculate the pH value of 0.0001 M #"HCl"# ?
1 Answer
Explanation:
Hydrochloric acid,
In order to calculate the pH of this solution, you need to know the concentration of hydronium cations.
The dissociation of the acid will produce
#"HCl"_ ((aq)) + "H"_ 2 "O" _ ((l)) -> "H"_ 3"O"_ ((aq)) + "Cl"_ ((aq))^(-)#
Here every mole of hydrochloric acid added to the solution will produce one mole of hydronium cations. In your case, you have
#["HCl"] = "0.0001 M" = 10^(-4)"M"#
This means that the concentration of hydronium cations is
#["H"_3"O"^(+)] = 10^(-4)"M"#
Plug this into the equation for pH
#color(purple)(bar(ul(|color(white)(a/a)color(black)("pH" = - log(["H"_3"O"^(+)]))color(white)(a/a)|)))#
to find the pH of the solution
#"pH" = - log(10^(-4)) = - (-4) * log(10) = 4.0#
The answer is rounded to one decimal place because you have one significant figure for the concentraiton of the solution.