Hydration Enthalpy of Sodium Hydride. 1

[bbqnw12]

Please, can anyone give me the actual value of the amount of heat given off (in KJ/mol) when Sodium Hydride reacts with water? And the stoichiometry of the reaction?

 

[kenvlach]

The reaction is

NaH(c) + H[sub]2[/sub]O(l) --> NaOH(aq) + H[sub]2[/sub](g)

The actual amount of heat increases with the amount of water available to dissolve the NaOH, but the dilution would temper any temperature rise. The &[ignore]Delta[/ignore];H[sub]Rxn[/sub] below uses the value for NaOH(aq, 400 H[sub]2[/sub]O):

&[ignore]Delta[/ignore];H[sub]Rxn, 25 C[/sub] = -112 + 0 –(-14) –(-68) = -30 kcal/mol

Data are from Perry’s, 7th ed.

 

[bbqnw12]

Thank you very much, kenvlach. Very helpful.

 

[bbqnw12]

Thank you very much, kenvlach. Very helpful.

 

[lloydbrown]

The heat of reaction is 10% less if your product is concentrated sodium hydroxide solution. NBS Circular 500 gives the heat of formation of sodium hydroxide as a function of dilution. For example,
  NaH(c) + 4 H2O(l) --> NaOH:3H2O + H2(g)

delH[sub]Rxn, 25 C[/sub] = -108.9 + 0 –(-13.7) –(-68.3) = -26.9 kcal/mol