An experiment was carried out to find the value of in hydrated calcium ethanedioate,

CHEMISTRY · Multi-part · A Level · Chemistry · Oxidation, reduction and redox reactions · Oxidation, reduction and redox reactions

Problem

An experiment was carried out to find the value of

n

in hydrated calcium ethanedioate,

\text{CaC}_2\text{O}_4\cdot n\text{H}_2\text{O}

. A

2.01\text{ g}

sample was dissolved in deionised water and made up to

250\text{ cm}^3

in a volumetric flask. When

25.0\text{ cm}^3

of this solution was acidified using an excess of dilute sulfuric acid, it reacted with

27.50\text{ cm}^3

0.0200\text{ mol dm}^{-3}

potassium manganate(VII). (1) Explain why the conical flask had to be heated during this titration. (2) Explain why, after a while, the manganate(VII) ions decolourised straight away. (3) Find the relative formula mass of hydrated calcium ethanedioate and the value of

n

Related theory

Stoichiometric Calculations
Redox Reactions
Oxidation number method
Balancing Redox Reactions
Oxidation and reduction

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