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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: linkamfai on May 23, 2015, 06:17:18 AM

Title: Silane burns
Post by: linkamfai on May 23, 2015, 06:17:18 AM

Why silane burns in contact with air, whereas methane requires a spark before it will combust ??? ???

Title: Re: Silane burns
Post by: Borek on May 23, 2015, 06:26:53 AM

You have to show your attempts at solving the question to receive help. This is a forum policy.

Have you heard a term "activation energy"?

Title: Re: Silane burns
Post by: linkamfai on May 23, 2015, 07:13:54 AM

Quote from: Borek on May 23, 2015, 06:26:53 AM

You have to show your attempts at solving the question to receive help. This is a forum policy.

Have you heard a term "activation energy"?

I'm sorry for against the policy.
Is that any reason(s), other than electronegative caused the different in activation energy?

Title: Re: Silane burns
Post by: Corribus on May 23, 2015, 10:59:39 AM

Flammability and pyrophoricity are complex properties and often are affected by factors not directly related to the compound itself (impurities, etc.). But a simplistic explanation can be had by considering that the combustion of either silane or methane requires in some way breaking an Si-H or C-H bond, and the rate of the reaction will depend on how much energy it takes to do this. Si-H bond is significantly weaker than C-H bond (for the silane/methane reactions, I find the bond enthalpy to be ~ 335 kJ/mol and ~ 432 kJ/mol, respectively). Can you think of a plausible reason why?