What is the value for º for the following reaction, given the standard entropy values? al2o3(s) + 3h2(g) → 2al(s) + 3h2o(g) –35 j/mol·k +35 j/mol·/k +179 j/mol·k –179 j/mol·k

179 (J/K*mol)

Explanation:

The value for ΔSºreaction for this reaction is calculated as follows:

2 * Sº of Al(s) + 3 * Sº of H2O(g) - 3 * Sº of H2(g) - S° of Al2O3(s)

that is, the subtraction of the standard entropy of the reactants to the products.

                                             |  Al(s)    |     H2O(g)   |  H2(g)    |    Al2O3(s)      

standard entropy (J/K*mol) | 28.3    |    188.825   | 130.684 |   50.92

So:

ΔSºreaction = 2*28.3 + 3*188.825 - 3*130.684 - 50.92 ≈ 179 (J/K*mol)

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

answersilicon (si); oxygen (o);