Two neutralisation reactions

High School Chemistry KS3 and KS4 Chemistry Two neutralisation reactions 1 calcium carbonate with hydrochloric acid 2 calcium hydroxide with hydrochloric acid A limestone chip was used for the first reaction which is mainly calcium carbonate. Powdered calcium hydroxide, sometimes referred to as slaked lime, was used in the second reaction, although the purity was not 100% and probably contained some calcium carbonate as one of the contaminants. Inthe video clip the reactions of a limestone chip and an equal mass of powdered calcium hydroxide with 0.1M hydrochloric acid are considered side by side. acid + base = salt + water acid + carbonate = salt + carbon dioxide + water Observations The limestone chip produces bubbles of colourless gas The powdered calcium hydroxide shows no visible signs of reaction - except in the case of the latter some initial bubbling was observed, probably due to contamination of the calcium hydroxide general purpose reagent with small amounts of calcium carbonate In any case, testing the pH of the two reaction mixtures with Universal Indicator paper after 5 minutes revealed the following - the limestone chip was still reacting slowly and the pH was 3 at best - the powdered calcium hydroxide had reacted much faster and this mixture showed a pH of at least 8 There is lots of chemistry to discuss here, including rates of reactions, neutralisation reactions, balanced symbol equations and much more.