This page describes how simple acid-base indicators work, and how to choose the right one for a particular titration. Litmus is a weak acid. It has a seriously complicated molecule which we will simplify to HLit. The "H" is the proton which can be given away to something else. The "Lit" is the rest This video will give you the basics of the back titration. A tricky but common twist to the typical titration question. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators Quick Reference. A technique in volumetric analysis in which a known excess amount of a reagent is added to the solution to be estimated. The unreacted amount of the added reagent is then determined by titration, allowing the amount of substance in the original test solution to be calculated. From: back titration in A Dictionary of Chemistry ». Back-Titration = a known amount of excess standard reagent is added to the sample. Then a second standard reagent is used to titrate the excess of the first reagent. A 0.2178 g sample of impure Mg(OH)2was dissolved in 50.00 mL of 0.1204 M HCl (1st standard reagent). Back-titration of the excess acid required 3.76 mL of 0.0948 M NaOH (2nd reagent). Back titration exercise 1. A 0.723 g sample of chalk (largely calcium carbonate) was dissolved in 20.0 cm 3 of 1.00 M hydrochloric acid. When the reaction was complete, the remaining acid was titrated with 0.500 M sodium hydroxide solution. The titre was 12.00 cm 3. What would be used to measure out the 20.0 cm 3 of hydrochloric acid? I use a writing frame to take you through three separate back titrations, teaching you the 5 basic steps that are generally involved.Private tuition online f Second important reaction used in the iodometry is reduction of iodine with thiosulfate: 2S 2 O 32- + I 2 → S 4 O 62- + 2I -. In the case of both reactions it is better to avoid low pH. Thiosulfate is unstable in the presence of acids, and iodides in low pH can be oxidized by air oxygen to iodine. Both processes can be source of titration errors. 1. Acid-Base Titration. The strength of an acid can be determined using a standard solution of a base. This process is called acidimetry. In the same way, the strength of a base can be found with the help of a standard solution of an acid, which is known as alkalimetry. Replacement of the water by chloride ions. In the presence of chloride ions (for example with chromium (III) chloride), the most commonly observed colour is green. This happens when two of the water molecules are replaced by chloride ions to give the tetraaquadichlorochromium (III) ion - [Cr (H 2 O) 4 Cl 2] +. back titration. A technique in *volumetric analysis in which a known excess amount of a reagent is added to the solution Access to the complete content on Oxford Reference requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription.