Question

Given the combustion of silane... `SiH_4(g)+2O_2(g)rarrSiO2(s)+2H_2O(g); DeltaH=−1429⋅kJ⋅mol^(−1)`.. How much heat will evolve given combustion of `15.7*g` quantity?

Answer 1

Approx. `700*kJ`

Explanation:

Thermochemical reactions ALWAYS quote enthalpy input/output PER MOLE OF REACTION AS WRITTEN:

`SiH_4(g) + 2O_2(g) rarr SiO_2(s) + 2H_2O(g)` `DeltaH=-1429*kJ*mol^-1`.

That is `-1429*kJ*mol^-1` of energy are involved when `1*mol`, `33*g` of silane are combusted to give stoichiometric silicon oxide, and water.

And thus we simply work out the molar quantity of silane:

`(15.7*g)/(32.12*g*mol^-1)=0.489*mol`

And `0.489*mol("of silane")xx-1429*kJ*mol^-1("of silane")` `=` `??kJ`.