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# Neutralisation reaction of ca watch

1. so the first equation is ca reacting with excess water and I need to find the ionic equation for it. However I am stuck.

Thanks
2. Strictly you can't neutralise (as per your title) with Ca as it isn't a base.

Have you done Kw? That's probably why you're confuzzled.

Anyhoo, Ca is reacting with H2O. H2O isn't ionic (it is a molecule) so you don't write it as ions.
3. (Original post by Pigster)
Strictly you can't neutralise (as per your title) with Ca as it isn't a base.

Have you done Kw? That's probably why you're confuzzled.

Anyhoo, Ca is reacting with H2O. H2O isn't ionic (it is a molecule) so you don't write it as ions.
What reaction would it be then when a metal reacts with an acid? I have done Kw already but doesn't ring any bell.

Thanks
4. The ionic equation of calcium + acid is Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g)
with water it is Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

I mention Kw as you would have learnt that some of the H2O will split up to H+ and OH-, but that can't be the explanation of what happens when Ca and water react

i.e. 2H2O -> 2H+ + 2OH-, then ignore the OH- and only consider Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g); the combined equations are the same as Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

The reason it can't be correct is that [H+] is sooo low that the reaction rate would be tiny, unless k were truly massive, but given the IE1&2 of Ca being so large, Ea must be fairly large too, and therefore k won't be massive.

Anyhoo, hopefully someone better at chemistry than me has read all that and might be able to tell me that I'm talking out of my bottom or on the right tracks.
5. (Original post by Pigster)
The ionic equation of calcium + acid is Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g)
with water it is Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

I mention Kw as you would have learnt that some of the H2O will split up to H+ and OH-, but that can't be the explanation of what happens when Ca and water react

i.e. 2H2O -> 2H+ + 2OH-, then ignore the OH- and only consider Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g); the combined equations are the same as Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

The reason it can't be correct is that [H+] is sooo low that the reaction rate would be tiny, unless k were truly massive, but given the IE1&2 of Ca being so large, Ea must be fairly large too, and therefore k won't be massive.

Anyhoo, hopefully someone better at chemistry than me has read all that and might be able to tell me that I'm talking out of my bottom or on the right tracks.
I thought you are a teacher, no? Now that you have mentioned Kw, it is a bit more confusing but in a nutshell H2o just doesn't dissociate in this reaction? Also what kind of reaction is this then ? Thanks
6. I have been teaching A level chemistry for ten years, but I only did 1st year chemistry at university (it wasn't needed for the degree I took).

If my guess is correct, the self-dissociation of water isn't terribly important in this reaction.

It is a redox reaction. The calcium is oxidised and the H in water is reduced. It can't be neutralisation, especially since OH- is being made. Neutralisations should involve H+ + OH- -> H2O.
7. (Original post by Pigster)
The ionic equation of calcium + acid is Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g)
with water it is Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

I mention Kw as you would have learnt that some of the H2O will split up to H+ and OH-, but that can't be the explanation of what happens when Ca and water react

i.e. 2H2O -> 2H+ + 2OH-, then ignore the OH- and only consider Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g); the combined equations are the same as Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

The reason it can't be correct is that [H+] is sooo low that the reaction rate would be tiny, unless k were truly massive, but given the IE1&2 of Ca being so large, Ea must be fairly large too, and therefore k won't be massive.

Anyhoo, hopefully someone better at chemistry than me has read all that and might be able to tell me that I'm talking out of my bottom or on the right tracks.
When the impossible is eliminated then only the improbable remains, Mr Bond.

1. The only species in water are water, hydrogen ions and hydroxide ions.
2. Hydrogen ions are by far the most reactive species.
3. Calcium needs to be ionised whatever happens, however the energy required to do so is compensated by the large hydration enthalpy of the calcium 2+ ion
4. Metals react with acids due to the high concentration of hydrogen ions.
5. Active metals react explosively with acids but far more slowly with water.

It is the hydrogen ions in water that are responsible for the redox reaction with active metals.
8. (Original post by charco)
When the impossible is eliminated then only the improbable remains, Mr Bond.

1. The only species in water are water, hydrogen ions and hydroxide ions.
2. Hydrogen ions are by far the most reactive species.
3. Calcium needs to be ionised whatever happens, however the energy required to do so is compensated by the large hydration enthalpy of the calcium 2+ ion
4. Metals react with acids due to the high concentration of hydrogen ions.
5. Active metals react explosively with acids but far more slowly with water.

It is the hydrogen ions in water that are responsible for the redox reaction with active metals.
I am lost, so which answer is right?
9. (Original post by coconut64)
I am lost, so which answer is right?
I believe that Sherlock holds the key ...
10. (Original post by charco)
I believe that Sherlock holds the key ...
I am serious, please just tell me what is the right answer. And what type of reaction this is. I will be thankful!
11. (Original post by charco)
When the impossible is eliminated then only the improbable remains, Mr Bond.
People who mix their metaphors really make my goat boil.
12. (Original post by Pigster)
It is a redox reaction. The calcium is oxidised and the H+ ions from water are reduced.
Corrected.

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