To calculate the enthalpy change for the synthesis of diborane from its elements, we need to determine the overall reaction using the given equations.
First, we need to write the overall reaction for the synthesis of diborane:
2B(s) + 3H2(g) = B2H6(g)
Then we can rearrange equations 1, 2, 3, and 4 to match the overall reaction:
-2 x (2: B2H6(g) + 3O2(g) = B2O3(s) + 3H2O(g)) = 2 x -2035kJ/mol = 4070kJ/mol
-3 x (3: H2(g) + 1/2 O2(g) = H2O(l)) = 3 x -286kJ/mol = -858kJ/mol
Adding these two equations together gives:
2B(s) + 3H2(g) = B2H6(g)
1: 2B(s) + 3/2O2(g) = B2O3(g) -1273kJ/mol
(2 x 4070kJ/mol) + (3 x -858kJ/mol) = 8140kJ/mol - 2574kJ/mol = 5566kJ/mol
Therefore, the enthalpy change for the synthesis of diborane from its elements is 5566 kJ/mol.
B2H6 is a highly reactive borane hydride that was once considered as a possible rocket fule for the US space program . Using the Hess's law, calculate the enthalpy change the for the synthesis of diborane from its element according to the equation
2B(s) + 3H2(g) = B2H6(g)
Reaction. Enthalpy change
1: 2B(s) + 3/2O2(g) = B2O3(g) -1273kj/mol
2: B2H6(g) + 3O2(g) = B2O3(s) + 3H2O(g) -2035kj/mol
3: H2(g) + 1/2 O2(g) = H2O(l) - 286kj/mol
4: H2O(l) = H2O(g) 44kj/mol
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