Electrolysis in ionic substances

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Homework Statement





Predicting the products of electrolysis
Ionic substances in solution break down into elements during electrolysis. Different elements are released depending on the particular ionic substance.


At the negative electrode, positively charged ions gain electrons. This is reduction, and you say that the ions have been reduced.

Metal ions and hydrogen ions are positively charged. Whether you get the metal or hydrogen during electrolysis depends on the position of the metal in the reactivity series:

the metal will be produced if it is less reactive than hydrogen
hydrogen will be produced if the metal is more reactive than hydrogen



i don't understand. exactly what does metal ions have to do with hydrogen ions?
 

Answers and Replies

  • #2
epenguin
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I suppose one way to think about it which should be supplemented by othera is is to say OK when you electrolyse copper sulphate solution in water you can get copper metal deposited. So if you electrolyse sodium chloride solution in water you should get sodium metal deposited. In water. What happens when you drop sodium metal in water? I hope you have seen it - not likely to forget.
 
  • #3
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What happens when you drop sodium metal in water? I hope you have seen it - not likely to forget.

heh. as a matter of fact i have not seen it?
 
  • #4
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The extraction of copper from copper ore is done by reduction with carbon. However, the copper produced is not pure enough for use as a conductor.

can somone please explain to me what the above statements mean?
 
  • #6
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errrr.... i don't really get the video......what are the white stuff formed at the end of the chemical reaction?
 
  • #7
Borek
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Do you know what is the reaction? Can you try to write reaction equation? If you are learning about electrolysis you should already know a little bit about chemistry, and reaction of sodium with water is one the most basic things (pun not intended (hint intended)) taught at chemistry courses.
 
  • #8
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nope, my school missed out on acids and alkalis, i learnt electrolysis based on chemical effects of an electric current. lol. but i have learnt how to form and balance chemical equations.
is it this: 2Na + 2H2O ----> 2NaOH + H2
 
  • #9
Borek
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2Na + 2H2O ----> 2NaOH + H2

That's right.

Now, there are two products. Which one is popping? Which can be a white solid?
 
  • #10
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um.... is sodium the white solid?
 
  • #11
epenguin
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Sodium is a soft metal - in this vid you can see them cutting it.


It is only shiny for a short time after it is cut, it is reactive and reacts with oxygen or I suppose moisture in the air to form a film.

Sodium reacts chemically with water liberating hydrogen which is what burns explosively the several videos you can see. Which is the next best thing to seeing it in the teaching lab which unfortunately you have not had. Seeing these things gives meaning and memorability to the theory which now you have to read up, we cannot write a textbook for you, find an elementary one,good luck :smile:. Chemistry does not get simpler than the chemistry of sodium so it was a good starting point.
 
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  • #12
Borek
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um.... is sodium the white solid?

I told you to look for PRODUCTS.
 
  • #13
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I told you to look for PRODUCTS.


uhhuh. but how do you expect someone like me who does not have any background knowledge on the chemical reaction between sodium and water to actually UNDERSTAND your questions which provide no further explanations? i was just making a guess, a harmless one. By the way, i would really appreciate it if you could be more patient with someone who seems like an idiot.
 
  • #14
Borek
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I am patient, I am trying to give you clear hints.

At this moment you know everything you need - you just have to apply this knowledge to the video.

Sodium is a metal, right? How do metal looks? Do they look like a white powder?
 
  • #15
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nope but all i saw were white sparks here and there.

sorry for my previous post, i admit i'm kinda short-tempered.
 
  • #17
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the white sparks are sodium hydroxide?
 
  • #18
Borek
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That's the only logical conclusion.
 
  • #19
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erm.... but where does this lead us to??
 
  • #20
Borek
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You asked about products of electrolysis - now imagine sodium is a product of electrolysis in water. Will such system be stable?
 
  • #21
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You asked about products of electrolysis - now imagine sodium is a product of electrolysis in water. Will such system be stable?

um i don't really get you. what do you mean by if such a system will be stable?
 
  • #22
Borek
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You have seen what happens when metallic sodium is put into water. Assuming metallic sodium is a product of water solution electrolysis - will it stay in the metallic form in water?
 
  • #23
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no? (um, i'm actually not sure so pls don't laugh>.<)
 
  • #24
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uh i found this:

an acid is a substance that produces H+ ions when dissolved in water.
when H+ ions are not present, the acid does not display the typical acid chemical properties.



hmmm the web says sodium is a base. so its doesn't produce H+ ions?
so its a base and is soluble in water??
 
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  • #25
Borek
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no?

That's a logical conclusion, isn't it? Sodium spontaneously reacts with water, if it would be an electrolysis product it would react with water immediately - so either it can't be a product, or even if it is, it reacts immediately and disappears (so it is not a product of the process).

uh i found this:

an acid is a substance that produces H+ ions when dissolved in water.
when H+ ions are not present, the acid does not display the typical acid chemical properties.

hmmm the web says sodium is a base. so its doesn't produce H+ ions?
so its a base and is soluble in water??

I must say you've lost me. Sodium is not a base, sodium is a metal. You were just shown how it behaves in water, you wrote a correct reaction equation (no H+ between products), now you write things as if you have never seen your own earlier posts.
 

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