The change in enthalpy when hf reacts with naoh in dilute condition is
Answers
Explanation:
Enthalpy changes of neutralisation are always negative - heat is given out when an acid and and alkali react. For reactions involving strong acids and alkalis, the values are always very closely similar, with values between -57 and -58 kJ mol-1.
That varies slightly depending on the acid-alkali combination (and also on what source you look it up in!).
Why do strong acids reacting with strong alkalis give closely similar values?
We make the assumption that strong acids and strong alkalis are fully ionised in solution, and that the ions behave independently of each other. For example, dilute hydrochloric acid contains hydrogen ions and chloride ions in solution. Sodium hydroxide solution consists of sodium ions and hydroxide ions in solution.
The equation for any strong acid being neutralised by a strong alkali is essentially just a reaction between hydrogen ions and hydroxide ions to make water. The other ions present (sodium and chloride, for example) are just spectator ions, taking no part in the reaction.
The full equation for the reaction between hydrochloric acid and sodium hydroxide solution is:
. . . but what is actually happening is:
If the reaction is the same in each case of a strong acid and a strong alkali, it isn't surprising that the enthalpy change is similar