if saline is NaCL (i.e one +ve to one -ve ion) why is it acidic?

Question

Normal Saline is said to have a pH of 5.5. Please explain chemically why this is the case

Answer 1

NaCl is not acidic. In the first reaction scheme above there is still effectively an OH- balancing the H+ so the addition of NaCl has no effect on pH. The tenuous clue might be the word "saline" which isn't necessarily pure NaCl. In the absence of any further information, I'd suggest that the most likely reason that NaCl dissolved in distilled water might have pH 5.5 in practice is because of dissolved CO2 from the air. CO2 forms carbonic acid when it dissolves in water:

CO2 + H20 = H2CO3

Answer 2

As the person above me said CO2 dissolves in water to form H2CO3. Even distilled water tends to have an acidic pH, as far as I know NaCl has no effect on the pH of a solution (certainly you can add it to a buffer without altering the pH). When you add HCl and NaOH you form NaCl and the solution is neutralised.

Saline solutions with a specific use are often buffered at the required pH.

Answer 3

The ions Na+ and Cl- have NO effect on pH so NaCl solutions are NOT acidic....as long as they are made up in DEIONIZED water that is. As others have said, the pH of distilled water is usually around 5.5 so in this case that is where the acidity comes from.
Other salts in solution DO have an effect on pH through a process called hydrolysis of salts...for instance, NH4Cl is acidic even in deionized water since NH4 + H2O = NH3 + H3O+ and H3O+ (hydronium ion) is acid!

Answer 4

NaCl dissolved becomes Na+ and Cl-.

Water contains an equal percentage of OH- and H3O+ ions, their relative concentration determines the acidity)

But the following reactions with water occur (equilibrium reactions)

1) Na+ + OH- <-> NaOH

2) Cl- + H3O+ <-> HCl + H2O

With 1), more NaOH is produced than HCl in 2) [Check tables], therefore eliminating more OH- than H3O+ from the liquid

Since more H3O+ will be present, the liquid will have an acidic character

Answer 5

The definition of Ph = -log [H+]

water is ph 7

H20 -----> H+ + OH- (reversible reaction)

adding NaCL will increase the concentration of H+ as shown in the persons answer above mine.
Thus an increase in H+ concentration will also lead to an increase in Ph. Hence a Ph which is lower than neutral water ie. slightly acidic.

Answer 6

the definition of an acid is anything that causes an H+ ion to be present when it the solution is mixed with water.
my guess is that the following equation would be the reaction:

NaCl + H2O ---> NaOH + H+ + Cl-

it would yield NaOH and aqueous hydrochloric acid, which would dissociate into Cl- ions and H+ ions.

Answer 7

The first answer was correct, except if it made NaOH, it would make an Alkali. Like he said, if it attached a H, it would make it acidic, but an OH would make it an Alkali, that's the difference...

I don't have an answer to your question, but I have a correction for that guy, incase you become misinformed...