200 ml of aqueous solution of HCl(pH=2) is mixed with 300 ml of an aqueous solution of NaOH(pH=12).what is the pH of the resulting solution?

1 Answer
Al E.
Jan 2, 2018

Let's find the concentrations of each,

#[HCl] = 10^-2"M"#
#[NaOH] = 10^-2"M"#

The key here is understanding that strong acids and bases completely dissociate into their ions. Thus, for hydrochloric acid the anti-log will do, and for sodium hydroxide we'd need the anti-log of pOH,

#14 - 12 = 2 = "pOH"#

From here it's a basic stoichiometry problem,

#NaOH(aq) + HCl(aq) to NaCl(aq) + H_2O(l)#
puu.sh

We're left with a relatively neutral salt and some strong base left, which will dictate the new pH,

#(0.001"mol")/(0.500"L") = 0.002"M"#
#therefore "pH" = 14+log[OH^-] approx 11.30#

I'm open to feedback if I made a mistake!

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