I've done an experiment with hydrochloric acid and magnesium ribbon, and in one of the questions I've been asked which is used as excess, I know what excess means but not sure I understand the question. Please can someone explain... The experiment was looking at the reaction rate with different concentrations of hydrochloric acid.
2007-04-24 07:41:45 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Excess means what you have more of. If the ribbon completely dissolved, then you must have hadd excess HCl. If only part of the ribbon dissolved, then you know there was not enough HCl to finish it off, so the ribbon must be in excess.
2007-04-24 07:45:11 · answer #1 · answered by Professor 1 · 0⤊ 0⤋
The one in excess is hydrochloric acid. It needs to be in excess so that you are sure that all the magnesium ribbon has reacted. Then using the chemical equation for the reaction and the mass of magnesium used, you can find the concentration of the acid.
2007-04-24 14:53:34 · answer #2 · answered by Weird.Beryl 3 · 0⤊ 0⤋
The excess is employed if it is difficult to determine the precise amounts of reactants to form products, or the reaction is subject to an equilibrium before sufficient product is formed. In the latter case, the excess "drives" the reaction further to completion. In your experiment, the ribbon was probably the excess because you want to see the response to a limiting amount of HCl.
2007-04-24 14:48:49 · answer #3 · answered by cattbarf 7 · 0⤊ 0⤋