Question

Aqua regia, a mixture of concentrated HNO₃ and HCl, was developed by alchemists as a means to "dissolve" gold. The process is a redox reaction with this simplified skeleton reaction: \mathrm{Au}(s)+\mathrm{NO}_{3}^{-}(a q)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{AuCl}_{4}^{-}(a q)+\mathrm{NO}_{2}(g) (b) What are the oxidizing and reducing agents?

Answer 1

a) Balanced equation;

$Au +3 NO^{-} _{3} +4Cl^{- }+6H^{+}$ ⇒ $AuCl^{-}_{4} + 3NO_{2} + 3H_{2} O$

b) oxidizing agent: N

    reducing agent: Au

a) The unbalanced redox equation is as follows:

$Au + NO^{-} _{3} +Cl^{- }+H^{+}$ ⇒ $AuCl^{-}_{4} + NO_{2} + H_{2} O$

Balance all atoms other than H and O.

$Au + NO^{-} _{3} +4Cl^{- }+H^{+}$ ⇒ $AuCl^{-}_{4} + NO_{2} + H_{2} O$

The oxidation number of gold changes from 0 to +3. The change in the oxidation number of gold is 3.The oxidation number of nitrogen changes from +5 to +4. The change in the oxidation number of nitrogen is 1.

So,

$Au +3 NO^{-} _{3} +4Cl^{- }+H^{+}$ ⇒ $AuCl^{-}_{4} + 3NO_{2} + H_{2} O$

Now balance O atoms on RHS,

$Au +3 NO^{-} _{3} +4Cl^{- }+H^{+}$ ⇒ $AuCl^{-}_{4} + 3NO_{2} + 3H_{2} O$

Now, balance hydrogen atoms on RHS,

$Au +3 NO^{-} _{3} +4Cl^{- }+6H^{+}$ ⇒ $AuCl^{-}_{4} + 3NO_{2} + 3H_{2} O$

This is the balanced chemical equation.

b) oxidizing agent: N

    reducing agent: Au

Learn more about oxidation number here;

brainly.com/question/12854037

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