How to find rate constant of reaction?

2016-08-02 5:46 pm

The reaction 4PH3(g)=P4(g)+6H2(g) is a first-order reaction with a half-life of 35 s. The rate constant of the reaction is _____ s^-1.

回答 (2)

2016-08-02 5:55 pm

For a first order reaction, half-life = ln(2) / k

The rate constant, k = ln(2) / half-life = ln(2) / 35 = 0.0198 s⁻¹

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2016-08-02 5:51 pm

Rate = k [P4]
Discount 'H2' a it will be in excess.

Hence
k = [P4 mol dm^-3] / rate (mol dm^-2 s^-1 )
Units cancel down to 's^-1'.

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