[narutodemonkill]

reaction has a rate constant k-2.80 L/mol*s
Initial concentration is 1.00 mol/l
the time require for 90% reaction is?

The way I did it was ln(.1/1)=-kt
solving for t I get 0.32 seconds but there is no option for this
it says the answer is 3.2 seconds?

[rabolisk]

First,I don't see how you get 0.32 seconds using the formula you give. Second, why isl n(.1/1) = -kt?

[samiam]

First order reaction

[rabolisk]

What makes you think this is a first order reaction?

[narutodemonkill]

What makes you think this is a first order reaction?

]

Question did not state if it was first or second order so I assumed it was first

[rabolisk]

It is not first order, and this is not a guess. The problem gives you one crucial detail that can be used to derive the order of the reaction.