(a) What is a redox reaction? Explain with example.(b) When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why?(c) In the reaction represented by the equation:MnO2 + 4HCl ----> MnCl2 + 2H2O + Cl2 (i) name the substance oxidised. (ii) name the oxidising agent.(iii) name the substance reduced. (iv) name the reducing agent.
(a) A redox reaction is one in which oxidation and reduction occur simultaneously in the reaction, i.e if one substance is reduced the other is oxidised.
$ZnO \ +\ C\ \rightarrow \ Zn + CO $
In the above reaction, C is oxidised as it has gained oxygen to form CO. and ZnO is reduced as it has lost oxygen to form Zn.
(b) When a magnesium ribbon burns in air with a dazzling flame and forms white ash, magnesium is oxidised because oxygen is added to magnesium.
$2Mg\ ( s) \ +\ O_{2}( g) \ \rightarrow \ 2MgO\ ( s)$
(c) $MnO_{2} \ +\ 4HCl\ \rightarrow \ MnCl_{2} \ +\ 2H_{2} O\ +\ Cl_{2} \ $
- The name of the substance oxidised- HCl is oxidised to Cl2
- The name of the oxidising agent- MnO2
- The name the substance reduced -MnO2 is reduced to MnCl2.
- The name of the reducing agent- HCl.
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