MgO + H2O what reaction is this and why?

stretch610

Hello,
I am baffled as to what reaction Magnesium oxide + deionised water is, i had it down to a redox reaction coz of the loss of oxygen from the H20 and gain of oxygen in final products
MgO + H2O = Mg(OH)2 + H2

all research i have done says this is not redox and i do not knw why. Any help would be great. and an explination of why it is a certain reaction as i need to understand why.

So, what's your definition of a redox reaction?

Reply 2

roar558

Are you sure that equation's right and balanced? If Mg(OH)2 is formed there would be no hydrogen as a product from your equation...

Reply 3

OP

Redox reaction as far as i know isnt just down to the loss and gain of electrons it is also down to the loss and gain of hydrogen and oxygen.
Oh and yeah balanced it should be
MgO + 2H2O = Mg(OH)2 + H2

Reply 4

stretch610

Redox reaction as far as i know isnt just down to the loss and gain of electrons it is also down to the loss and gain of hydrogen and oxygen.
Oh and yeah balanced it should be
MgO + 2H2O = Mg(OH)2 + H2

That's where your definition slightly faulters. Oxidation Is Loss of electrons. Reduction Is Gain of electrons. The loss and gain of electrons will result in the change of an element's oxidation number. If there is no change to any element's oxidation number, like in the above equation, it is not a redox reaction.

The equation describes ionic bonding.

The idea of losses and gains of hydrogen and oxygen might have been a method used to help describe a redox reaction but inevitably leads to misinterpretation so it's best to stick with the definition.

Reply 5

OP

Yeah that is the main definition i know but ionic bonding is not the answer, it has to be a reaction i has coverd in this unit y tutor tells me and i have coverd redox and acid base , seen as there is no acid it must be redox. are you sure there is no change in O.N from reactants to products?

Reply 6

stretch610

Yeah that is the main definition i know but ionic bonding is not the answer, it has to be a reaction i has coverd in this unit y tutor tells me and i have coverd redox and acid base , seen as there is no acid it must be redox. are you sure there is no change in O.N from reactants to products?

I'm pretty sure it's ionic bonding. It's not acid-base as water is neutral. There isn't a change in oxidation number in any of the elements, balance the charges yourself and you will see.

Reply 7

hardz21

That reaction is wrong. The equation is actually :
MgO + H2O -> Mg2+ + 2OH-
forming alkaline solutions
And it to get an hydroxide it would be
Mg + H2O -> Mg(OH)2 + H2
Which is the action of water, also called hydration I think?

Reply 8

hardz21

stretch610

Redox reaction as far as i know isnt just down to the loss and gain of electrons it is also down to the loss and gain of hydrogen and oxygen.
Oh and yeah balanced it should be
MgO + 2H2O = Mg(OH)2 + H2

This isn't balanced
On the products side there are 2 Oxygens (O)
On the reactants side there are 3 Oxygens (O)

Reply 9

OP

Yeah ok rewriet the equation MgO + H2O = Mg(OH)2 balanced

Im confused as to how if the oxidation numbers dont chnage you say it is ionic bonding?? isnt ionic bonding to loss and gain of electrons? which would indicate redox reaction.
Any help to what kind of reaction is actually taking place would be much appreciated!

Reply 10

OP

What chemical reaction is happening in this equation?
MgO + H2O = Mg(OH)2

Reply 11

stretch610

Yeah ok rewriet the equation MgO + H2O = Mg(OH)2 balanced

Im confused as to how if the oxidation numbers dont chnage you say it is ionic bonding?? isnt ionic bonding to loss and gain of electrons? which would indicate redox reaction.
Any help to what kind of reaction is actually taking place would be much appreciated!

Mg(OH)2 is definitely an ionic compound but so is MgO. The charges on the LHS for Mg is +2 and for O it's -2, for H it's +1. The RHS is the same for the equation to be balanced. As for name of equation, I would go with hydration too.

Reply 12

EierVonSatan

21

A synthesis reaction, I suppose.

Reply 13

boromir9111

17

I am sure there is a thread on this already which has been answered :s-smilie:

redox

OP

I say redox and hydration . but im stuck as to the reason why its a redox other reduction and oxidation in terms of oxygen loss or gain.It is a reversible hydration reaction.

boromir if it has been amswerd help me out and give me the answer haha!

Reply 16

oceane

10

Hydrolysis of a salt. I.e the reverse of an acid + base reaction.

Reply 17