Adecomposition reaction has a rate constant of 0.0012 yr^-1
(a) what is the half-life of the reaction?
(b) how long does it take for [reactant] to reach 15% of its original value?

A) 577.6 years

B) 1580.9 years

Explanation:

You can know the order of a reaction given the units of the rate constant:

Then we know that this is a first order reaction because years is a unit of time as well as seconds. The half life of a first order reaction is given by:

Here you can solve for the half life:

Now for the rate law for a first order reaction is:

Then, if you want to know how long does it take to reach a certain value you solve for time:

The 15% of its original value is

You solve for time:

Hope it helps!

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c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current