[TF2]

Hi i got a really important question regarding reducing agent

Gold does not react with nitric acid or hydrochloric acid but with a combination of both called aqua regia. Identify the reducing agent in the following equation:
Au(s) + 4H+ + NO3 + 4Cl ---> [AuCl4] + 2H2O + NO(g)
a) NO3
B)Au
C)H+
D)Cl-
E) The reaction is not a redox reaction

Thx

[Astrokel]

What's a reducing agent?

[TF2]

a substance that has been reduced

[Donaldson Tan]

TF2 is wrong. A substance is said to be reduced when it accepts an electron transfer. The substance of which the electrons originate from is said to be the reducing agent.

For example, in the case of:
Fe (s) + Cu²⁺ (aq) -> Fe²⁺ (aq) + Cu (s)

The oxidation number of Cu decreases from +2 to 0, thus Cu is reduced. Cu²⁺ (aq) accepted the electrons from Fe to be Cu (s), thus Fe (s) is the reducing agent in the abovementioned example.

[TF2]

can you help me with my question please

[Borek]

Assign oxidation numbers to all elemenets in the reaction, see which get oxidized and which get reduced. Geo explained how to do it.

[Arkcon]

can you help me with my question please

Sure

a substance that has been reduced

In your reaction:

Au(s) + 4H+ + NO3 + 4Cl ---> [AuCl4] + 2H2O + NO(g)

What is being oxidized?  What is being reduced?  What is gaining electrons?  What is losing them?  What is changing, from free elemental form, to end up with more electrons, shared with other atoms?  These are all hints, you can use, in addition to oxidation number, to help you solve this problem, and others like it.

[TF2]

ok thx for the hlp....im getting NO3 from my question. Is this right?

[Fleaker]

I do this reaction a lot

It would seem that you don't have proper charges assigned to some of your anions, or much of anything for that matter. Try rewriting your equation.

Also, as a hint, NO and NO₃ aren't really formed in this reaction--a heavier, toxic read brown gas is the principle product*


*in reality, there are many nitrogen oxides produced from aqua regia's action on a metal.