when we put a salt eg NaCl into an acidic solution eg HCl, does the pH value of thr solution decrease since NaCl is neutral whilr HCl is acidic. bt cos there isnt any chemical reaction so im unsure.
this is wat t think: thr pH value of the entire solution decreases while the pH of thr acid and salt doesnt change. is that right?
thanks for the helpf
Originally posted by SgStudentStressed:when we put a salt eg NaCl into an acidic solution eg HCl, does the pH value of thr solution decrease since NaCl is neutral whilr HCl is acidic. bt cos there isnt any chemical reaction so im unsure.
this is wat t think: thr pH value of the entire solution decreases while the pH of thr acid and salt doesnt change. is that right?
thanks for the helpf
pH is for a solution, it doesn't matter whether the solution contains a mixture of acids, a mixture of salts, or a mixture of salts and acids.
Although not tested at 'O' levels, it may help your understanding, to be aware that pH may be taken to be -log10 [H+] where [H+] = molarity (ie. molar concentration) of protons (ie. H+ ions).
Say you have 500cm3 of 0.5mol/dm3 of HCl mixed with 500cm3 of 1mol/dm3 of NaCl. What is the pH of the solution mixture? Since volume is doubled, molarity of protons is halved, ie. [H+] = 0.25mol/dm3. Key in -log10(0.25) into the calculator, and you get 0.6 as the pH of the solution.
Since the acid and the salt have already been mixed, the sentence "what is the pH of the acid" is incorrect, as is the sentence "what is the pH of the salt". The only question that can ask you is, "what is the pH of the resulting solution of the mixture of acid and salt?" for which you can calculate the answer as described in the preceeding paragraph.
ok let me rephrase my qns
Some table salt NaCl is placed into a beaker containing HCl. what will the final pH value be taking that they are used in the same molarity
just to make it simple, is this principle right?
when i add neutral or basic substance into an acidic substance the pH value of the entire solution would increase making it less acidic and more alkaline
e.g. put a specific amount of NaCl into HCl and the pH of the entire solution changes from 2 to 4,5
when i add neutral or acidic substance into an alkaline substance the pH value of the entire solution would decrease making it less alkaline and more acidic?
e.g. put a specific amount of NaCl into NaOH and the pH of the entire solution changes from 14 10.5
Originally posted by SgStudentStressed:just to make it simple, is this principle right?
when i add neutral or basic substance into an acidic substance the pH value of the entire solution would increase making it less acidic and more alkaline
e.g. put a specific amount of NaCl into HCl and the pH of the entire solution changes from 2 to 4,5
when i add neutral or acidic substance into an alkaline substance the pH value of the entire solution would decrease making it less alkaline and more acidic?
e.g. put a specific amount of NaCl into NaOH and the pH of the entire solution changes from 14 10.5
Correct, IF all species are aqueous, rather than solid. It's simple dilution.
huh i dont eeally get what ur trying to say
but is my principle right?
Originally posted by SgStudentStressed:but is my principle right?
Yes.
wait so if i put solid NaCl into aqueous HCl (hydrochloric acid) will there be any change in pH
Originally posted by StudentQns:wait so if i put solid NaCl into aqueous HCl (hydrochloric acid) will there be any change in pH
Nope.