L O.

asked • 07/21/14

questions about chemical reaction

I need to find the chemical formula for the reactant which gives up a hydrogen ion in this reaction.
 
         CaO + H2O        →    Ca2+   +  2OH-
 
I also need to find the chemical formula for the reactant which accepts a hydrogen ion in the reaction.
 
thanks for explaining.

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Kathleen C. answered • 07/23/14

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I can see that you are trying very hard.  Look back up at the clues to help you -- you are almost there.
The reactant that is acting as an ACID is H2O
The reactant that acts like a base is CaO, because it ionizes into negative oxygen ions, which strongly attract protons.
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L O.

So I do not know if I have this backwards or not.
 
CaO gives up the hydrogen ion and H2O is accepting the hydrogen ion???
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07/24/14

Carol E. answered • 07/21/14

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L,
 
Here's a hint that might hep you.  When CaO is dissolved in H2O, the following happens.
 
CaO ----> Ca2+   +  O2-
 
One of these ions goes on to react with H2O.  Do you see which one?
 
 
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L O.

would it be H + ion for the reactant that gives up a hydrogen?
 
would it be H2O for the reactant that accepts the hydrogen?
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07/21/14

Carol E.

Take another look.  What do you think the O2- ion does that was shown in the hint?
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07/21/14

L O.

would it accept the hydrogen so then  formula would be H30 ?
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07/21/14

Carol E.

You're right that O2- accepts a proton, which means it is acting as a base.  If water is the acid, what is the product of this reaction
 
O2- + H2O ----->  ?
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07/21/14

L O.

Okay I am really trying so please be patient with me,
 
the chemical formula which gives up a hydrogen ion is H3O
 
the chemcial formula which accepts a hydrogen ion is H + ion
 
the chemical formula  which behaves like an acid is C2HO
 
Does the formula for the reactant that acts like a base in this reaction is it H + ion
 
 
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07/22/14

Carol E.

To help you understand, let's review two definitions.
 
An ACID is any substance (molecule or ion) that donates a proton (H+ ion) to another substance.  To be an acid, the substance must have a hydrogen atom it can lose as an H+ ion.
 
A BASE is any substance (molecule or ion) that accepts a proton (H+ ion).  To be a base, the substance must have a non-bonding pair of electrons to bind the  H+ ion.
 
Going back to the reaction
 
CaO + H2O ----->  Ca2+ + 2OH-
 
you had to identify which substance donates a proton (acts as an acid) and which substance accepts a proton (acts as a base).  On the reactant side of the arrow, the only substance that contains a proton is  H2O, so it must be the acid.  
So then which substance on the left side of the arrow is the base?  In both CaO and H2O the oxygen atoms have unshared pairs of electrons, so  it seems either one could be the base.  This is where the hint comes in:
 
CaO -----> Ca2+  + O2-  
 
The oxide  ion (O2-) is a very strong base, much stronger than H2O.  Your textbook should have a table of relative acidities similar to the one in this link to help you to this answer.
 
http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter15/Text_Images/FG15_01-01TO1.JPG
 
To summarize,
 
CaO + H2O ------> Ca2+  + 2OH-
 
involves 2 reactions. First,
 
CaO -----> Ca2+ + O2- ( CaO separates into  ions in water)
 
Then, second,
 
O2-  + H2O ------> 2 OH- (Water acts as an acid, transferring one of its protons to the oxide ion which acts as base)
 
I hope you find the details helpful.
 
 
 
 
 
 
 
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07/22/14

L O.

okay I think I am getting closer to understanding.
 
the chemical forumla for the reactant that behaves like a base in this reaction is H2O
 
it is an aqueous acid solution because the aqueous solution is an acid base since the hydrogium ion, H3O, is an acid.
 
the pH level is less than 7
 
99.5% of the molecules in this aqueous solution do not ionize. so this solution the flow would be weak since it is a weak acid and does not have a good conductor of electrical current.
 
 
I hope I am now correct with these
 
the formula for the reactant that gives up the hydrogen ion is H2O base
 
the formula for the reactant that accepts a hydrogen ion is H + ion
 
Is the chemical formula for the reactant that behaves like an acid still C2H  O2
 
thanks.  i am trying really hard
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07/22/14

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