Identify the metal which undergoes these reactions

In summary, the conversation discusses how to determine the correct compound in a chemical reaction by considering the properties of the metals involved and looking at the color of the precipitate formed. The conversation also addresses questions about the solubility and amphoteric properties of certain compounds. Through this process, the participants are able to eliminate tin, lead, and magnesium as potential compounds and determine that the compound in question is zinc.
  • #1
TT0
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Homework Statement


Screen Shot 2016-07-02 at 11.23.24 AM.png


Homework Equations

The Attempt at a Solution


The only thing that helped me was that with excess NaOH, the white precipitate dissolves. The only compounds I know that do this are zinc hydroxide and aluminium hydroxide. However, I don't know how the other reactions will help me decide between the two. Could someone explain this?

Cheers!
 
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  • #2
Check properties of the metals involved. For example - last step is clearly precipitation of the sulfide. What color is a lead sulfide?
 
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  • #3
Lead sulfide is black according to google images. So I guess it is eliminated. Magnesium definitely wouldn't be it because it won't form a precipitate as a hydroxide.

This leaves us with zinc, aluminium and tin. Googling each of the sulfides, I can eliminate tin sulfide as it is not white. I don't really know where to go from here, I tried to look at the properties of the metals but I still don't know. In the last reaction, why is H2S on the top and NaOH on the bottom. Is the H2S a catalyst? I think knowing this might help.

Cheers!
 
  • #4
TT0 said:
Magnesium definitely wouldn't be it because it won't form a precipitate as a hydroxide.

Check that.
 
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  • #5
I see, my solubility rules was wrong. Group II hydroxides are only slightly soluble. I got confused because they are also strong bases, yet they are only slightly soluble?

Magnesium sulfide is soluble and forms hydrogen sulfide and magnesium hydroxide. But as there are already hydrogen sulfide and magnesium hydroxide, I guess ti will precipitate. So magnesium is the answer?

Thanks!
 
  • #6
No, as magnesium sulfide is soluble.
 
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  • #7
In the first 3 reactions, the amphoteric reactions are happening right? This leaves zinc and aluminium as they are the ones that display these properties. When I googled zinc and aluminium sulfide, it seems both are white compounds. How do you differentiate between them?

Thanks!
 
  • #8
I don't think you can precipitate aluminum sulfide from water solutions - it decomposes on contact with water.
 
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  • #9
I see, so the answer is zinc. Thanks for all the help!
 

1. What are the common types of reactions that metals undergo?

Metals can undergo a variety of reactions, but the most common types are oxidation, reduction, displacement, and combination reactions.

2. How can I identify the metal in a reaction?

To identify a metal in a reaction, you can perform various tests such as the flame test, acid test, or conductivity test. These tests help determine the physical and chemical properties of the metal, which can then be used to identify it.

3. What are some indicators that a metal is undergoing a chemical reaction?

Some indicators that a metal is undergoing a chemical reaction include changes in color, formation of gas or precipitate, release of heat or light, and changes in physical properties like density or melting point.

4. Can two different metals undergo the same reaction?

Yes, two different metals can undergo the same reaction, as long as the conditions are suitable for that specific reaction to occur. For example, both iron and zinc can undergo a displacement reaction with hydrochloric acid.

5. How does the reactivity of a metal affect its reactions?

The reactivity of a metal plays a crucial role in determining the types of reactions it can undergo. More reactive metals tend to have stronger reactions and can displace less reactive metals in displacement reactions.

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