<p>a solution of sodium flouride is added to a solution of hydrochloric acid.
The answer key gives (H+) + (F-) for the reactant and HF for the product, but shouldn’t the HF in the product also become (H+) and (F-) since HF is aqueous?</p>
<p>HF is a weak acid. it doesn’t ionize (it does, but very little)</p>
<p>so when you do reactions, you always leave it as HF</p>
<p>how can you tell it’s a weak acid?</p>
<p>In another reaction problem, “excess concentrated ammonia is added to a solution of nickel(2) bromide”, what shoud the compound be if the reactands are EXCESS CONCENTRATED ammonia and a solution of nickel(2) bromide?</p>
<p>you have to memorize the weak acids. (HF, CH3COOH, etc.) until you learn the rules and trends for what makes something a weak acid as opposed to a strong acid.</p>
<p>if i remember correctly it is mostly because fluorine is such a small element and has such a high electronegativity that it holds on tightly to the hydrogen atom, causing it not to ionize when placed in a solution.</p>
<p>however you probably haven’t gotten to the acids and base section, you’ll learn all about the ionization of weak acids and bases in that unit… the acid dissociation constant, Ka.</p>
<p>just saw your other problem.</p>
<p>for the most part, whenever a reaction is run in excess it basically just means that there is enough of the substance for the reaction to run to completion (so that you don’t have to go in and fine the limiting, etc.)</p>
<p>There’s a list of strong acids you can memorize. So if something is not in the list of strong acids, it’s a weak acid.</p>
<p>acetic acid CH3OOH i believe and HF are the weak acids they test, NH3 ammonia is a weak base, like ^ said the other way is to simply remember all of the strong bases and acids, what is not strong is weak.</p>