energy balance of 2 Na(s) + 2 H2O(l) => 2 NaOH(aq) + H2(g)

[dijinj]

NaOH(s) + H₂O(l) => Na+ + OH- + H₂O + HEAT

2 Na(s) + 2 H₂O(l) => 2 NaOH(aq) + H₂(g)

 

Is the second reaction exothermic? How to calculate energy balance of both reactions?

 

[caters]

No the second reaction requires heat whereas the first one doesn't.

 

NaOH is a strong base with a pH of 14 at normaility 1.

 

This means that it will naturally, without any heat required dissasociate into Na⁺ and OH^-.

 

the OH bonds with any H⁺ from the autoionization of water.

 

The Na⁺ stays dissolved.

 

NaOH is ionic so it dissolves in water.

 

However to get Na⁺ and H2O to form NaOH and H2 will require heat because naturally they don't want to do that so because the 2nd reaction requires heat it is endothermic whereas one that is exothermic will produce heat and not require it. That is how our sun gets its heat is from exothermic reactions.

Edited May 28, 2014 by caters

[hypervalent_iodine]

No the second reaction requires heat whereas the first one doesn't.

 

NaOH is a strong base with a pH of 14 at normaility 1.

 

This means that it will naturally, without any heat required dissasociate into Na⁺ and OH^-.

 

the OH bonds with any H⁺ from the autoionization of water.

 

The Na⁺ stays dissolved.

 

NaOH is ionic so it dissolves in water.

 

However to get Na⁺ and H2O to form NaOH and H2 will require heat because naturally they don't want to do that so because the 2nd reaction requires heat it is endothermic whereas one that is exothermic will produce heat and not require it. That is how our sun gets its heat is from exothermic reactions.

Er, no. Have you ever seen sodium hit water before? It's pretty exothermic. Perhaps you should avoid answering questions if you're unsure of them yourself.

 

OP: Do you require numerical answers for delta H or something? You haven't provided enough information to do that, if so. Some clarification on the exact question and the information you are given would be helpful here.

[dijinj]

will electrolysis donate an electron to Na+ and can Na be deposited on cathode. I know this require some energy but how to calculate it, can you suggest good references for calculating energy balance?

[Fuzzwood]

No, doesn't happen in water. Kindly study some chemistry.

[Enthalpy]

The heat of reaction is computed from a table that lists the "enthalpy of formation" (search keyword) of the compounds. This enthalpy is computed with reference to the elements in their normal state, so for the second line of the original post, it takes only the values for liquid H₂O (-285.8kJ/mol) and for aqueous NaOH (find for instance the enthalpy of formation of solid NaOH (-425.6kJ/mol) and its enthalpy of dissolution).

 

Energy for free: no, the energy needed to regenerate metallic sodium exceeds what you get from reacting it.

[imatfaal]

!

Moderator Note

 

Wild speculation regarding free energy from the two reactions has been split off to speculations.

 

Please keep the main science fora for sensible and serious discussion within the current framework of known science.

 

http://www.scienceforums.net/topic/83528-free-energy-from-sodium-hint-it-doesnt-work/