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Fig. 15. Titration plot of back-titration of excess EDTA with Cu(II) in NH 3 /NH 4 Cl buffered solution. Direct EDTA titrations with metal ions are possible when reaction kinetics are fast, for example zinc, copper, calcium and magnesium. However, with slower reaction kinetics such as those exhibited by cobalt and nickel, back-titrations are used.
The A-Level grades were announced in England, Wales and Northern Ireland on 13 August 2020. Nearly 36% were one grade lower than teachers' predictions and 3% were down two grades. [14] [15] By comparison, 79% of university entrants in 2019 did not achieve their predicted grades. [15]
Edexcel (also known since 2013 as Pearson Edexcel) [2] is a British multinational education and examination body formed in 1996 and wholly owned by Pearson plc since 2005. It is the only privately owned examination board in the United Kingdom. [3] Its name is a portmanteau term combining the words education and excellence.
[3] [4] In June 2011 Edexcel announced that the AEA was being extended further for mathematics, until June 2015, which was later extended until 2018. [ 5 ] In 2018, Edexcel introduced a new specification, meaning the Advanced Extension Award in mathematics would continue to be available to students in 2019 and beyond, as a qualification aimed ...
Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated. A back titration is useful if the endpoint of the reverse titration is easier to identify than the endpoint of the normal titration, as with precipitation reactions
In analytical chemistry, argentometry is a type of titration involving the silver(I) ion. Typically, it is used to determine the amount of chloride present in a sample. The sample solution is titrated against a solution of silver nitrate of known concentration. Chloride ions react with silver(I) ions to give the insoluble silver chloride:
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If boric acid (or some other weak acid) was used, direct acid–base titration is done with a strong acid of known concentration. HCl or H 2 SO 4 can be used. Indirect back titration is used instead if strong acids were used to make the standard acid solution: strong base of known concentration (like NaOH) is used to neutralize the solution. In ...