Metal oxides changeing acidity

  • #1
When Metals (specifically Magnesium) oxidise within water would this increase or decrease the accidity of the water around it?
 

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  • #2
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When Metals (specifically Magnesium) oxidise within water would this increase or decrease the accidity of the water around it?

Here are two (unbalanced) reactions:
CaO + H2O ---> Ca(OH)2
Na2O + H2O ---> NaOH

Does that make the answer evident?

(OK: the first one is balanced, but only by accident.)
 
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  • #3
Here are two (unbalanced) reactions:
CaO + H2O ---> Ca(OH)2
Na2O + H2O ---> NaOH

Does that make the answer evident?

(OK: the first one is balanced, but only by accident.)

Yeah I think so. So the reaction involved would be MgO + H2O ---> Mg(OH)2

And this is basic because of the hydroxide? Right?

(this is actually the opposite to what i would've thought based upon the results of the experiment I did)
 

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  • #4
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Yeah I think so. So the reaction involved would be MgO + H2O ---> Mg(OH)2

And this is basic because of the hydroxide? Right?

(this is actually the opposite to what i would've thought based upon the results of the experiment I did)

Yes: Magnesium hydroxide will dissolve in water to increase the [OH-], and that is one of the definitions of a base.

I am more used to using a pH meter than the test strips (nor can I read the writing on the strips). What was the experiments and what ere the results?
 
  • #5
Yes: Magnesium hydroxide will dissolve in water to increase the [OH-], and that is one of the definitions of a base.

I am more used to using a pH meter than the test strips (nor can I read the writing on the strips). What was the experiments and what ere the results?

I hope that's easier to see. - - The experiment was run to test/prove that magnesium used in a Daniell Cell was also reacting with the magnesium nitrate used as one of the electolytes. On the graph of voltage recorded against temperature it was found that the results from about 75 degrease Celecius upwards the voltage was very inconsistant, yet from below 75 degrease the voltage (aproximatley) decrease uniformely. We thought this to be due to the magnesium forming bubbles around itself because it was reacitng with the magnesium nitrate.

The experiment was sugested to us by our teacher he said we should test the PH levels of magnesium within heated water and see if the PH levels change because when a metal oxidises it should change the PH levels of the surrounding water.

The results arn't entirely clear because as you can see it's hard to see much of a change at all in the colour of the paper, but when the magnesium and water are heated the paper does appear to get darker - suggesting that the water became more acidic, the opposite of what should thoretically happen.

I don't think the school has any PH metres which sucks. We havn't actually completed the experiment yet we just ran this initial test to see if a result could be achieved and i can't run another test for a while because it's currently holidays.
 

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  • #6
Sorry i just checked on the internet and i actully copied something down wrong, turns out the darker the colour the closer to 14 it becomes so the result actually shows the experiment getting more basic, which makes sense.

EDIT: How does a PH metre work, does this give you an actual reading?
 
  • #8
Thanks Borek and Fewmet for the responses.

Just wondering I was thinking of borrowing a PH metre from one of my freinds who owns a pool, do you think this would be suitable to use in a lab experiment like the one mentioned above?
 
  • #9
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36
I've never used a pH meter for a pool. It might not cover as broad a range of pH as you need, but you can check thou out online if you know the manufaturer.

You could also find pH precisely with a titration using an indicator.
 
  • #10
Borek
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You could also find pH precisely with a titration using an indicator.

No, you can't. Titration can be used to determine amount of acid, but not pH.
 
  • #11
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No, you can't. Titration can be used to determine amount of acid, but not pH.

Of course...thanks for catching that.
 
  • #12
Yeah, I think it'll work according to the PH paper the levels didn''t change much and I think i'm only looking at a range from about 6-8.
 

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