Sulfuric Acid & Gold: Does it React?

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In summary, the conversation discusses the lack of reaction between concentrated sulfuric acid and gold, despite the oxidation potential of sulfur in concentrated H2SO4 being higher than that of gold. The experts suggest rechecking the standard reduction potentials for acidic sulfuric acid and metallic gold, and balancing the half reactions to find the resulting new "E" value. It is concluded that more energy is needed to dissolve gold in sulfuric acid than what is provided by the acid alone. There is also a mention of the potential of S2O7 in oleum, but further clarification is needed to fully understand the situation.
  • #1
haiha
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Hi everybody
I know that concentrated sulfuric acid doesn't react gold. But I am puzzled because the oxidation potential of sulfure in concentrated H2SO4 is even higher than that of gold. Could anyone help me please.
Thanks
 
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  • #2
haiha,
Recheck the standard reduction potentials for acidic sulfuric acid and of metallic gold. Which one would more tend to want to be in reduced form?

1 sulfate + 4 H+ + 2e -----> sulfurous acid + 1 water, E = +1.5 v

1 auric(+3) + 3e -----> 1 gold in reduced metal form, E = +.17 v

Now, I forgot how the rest of this works, but you probably want to balance the two half reactions and find the resulting new "E" value; and you will find that it is negative, meaning the reaction is not spontaneous. You must use more energy in order to dissolve the gold than would be provided just from sulfuric acid.
 
  • #3
Thanks symbolipoint for answering me. But when i check in the manual, the potential of S2O7 (which is in oleum) is about 1.9-2.0 v (i don't remember exactly), and that is higher than that of metalic gold.
 
  • #4
haiha said:
Thanks symbolipoint for answering me. But when i check in the manual, the potential of S2O7 (which is in oleum) is about 1.9-2.0 v (i don't remember exactly), and that is higher than that of metalic gold.

Your comments there aren't exactly so clear. Are you giving the "oleum" reduction potential or are you giving it as an oxidation potential? What is the expected other form starting from "oleum"? Be aware, oleum is a solution of sulfur trioxide in sulfuric acid; no water is present. Would you give the exact electrochemical potential involving oleum? That might help see the situation more clearly. (I could not find that in an online search and it's not in my old textbook).
 

1. What happens when sulfuric acid and gold react?

When sulfuric acid and gold react, the gold is oxidized and dissolves into solution, forming gold ions. This reaction is known as gold dissolution or gold leaching.

2. Will sulfuric acid react with all forms of gold?

Yes, sulfuric acid can react with all forms of gold, including pure elemental gold and gold compounds such as gold chloride or gold sulfide.

3. Does the concentration of sulfuric acid affect the reaction with gold?

Yes, the concentration of sulfuric acid can affect the rate of reaction with gold. Higher concentrations of sulfuric acid can result in a faster reaction and higher dissolution rate of gold.

4. Is the reaction between sulfuric acid and gold exothermic or endothermic?

The reaction between sulfuric acid and gold is exothermic, meaning it releases heat. This is due to the strong chemical bonds formed between sulfuric acid and gold ions.

5. Are there any safety precautions to take when working with sulfuric acid and gold?

Yes, both sulfuric acid and gold can be hazardous, so it is important to wear proper protective gear such as gloves, goggles, and a lab coat. It is also important to work in a well-ventilated area and handle both substances with caution to avoid any accidents or exposure.

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