Question

Which ions are present when hydrochloric acid has exactly neutralized aqueos sodium hydroxide?(A )Na+,Cl-,H+ and OH- (b) Na +,Cl- and H+ (C) Na + and OH- (D)H+ and OH- Why is it A? DONT KNOW TELL ME.

Answer 1

(A) `Na^+`, `Cl^-`, `H^+`, `OH^-`.

Explanation:

Hydrochloric acid is basically an aqueous solution of `HCl`—which is water, except with dissociated `H^+` cations and `Cl^-` anions which came from `HCl`.
The same thing applies for sodium hydroxide—it is a solution which contains dissociated `Na^+` and `OH^-` ions.

When `HCl(aq)` and `NaOH(aq)` react, the balanced equation for their reaction would be like this:

`HCl(aq) + NaOH(aq) -> H_2O(l) + NaCl(aq)`

But we know that `HCl(aq)` is basically `H^+(aq)` and `Cl^(-)(aq)`, and `NaOH(aq)` is basically `Na^+(aq)` and `OH^(-)(aq)`, so the complete ionic equation would be this:

`H^+(aq) + Cl^(-)(aq) + Na^+(aq) + OH^(-)(aq) -> H_2O(l) + Na^+(aq) + Cl^(-)(aq)`

From this equation, we would probably think that the answer to the question is `Na^+` and `Cl^(-)`, because they're the only ions present after the reaction occurs.
But that's not an answer choice.

So, the question must be asking about the ions that are present both before and after the reaction occurs—which would include `H^+` and `OH^-`.

Our answer would then be: `Na^+`, `Cl^(-)`, `H^+`, and `OH^-`.