How long will it take for the concentration of ammonia to drop from 1.25 M to .388 M for the zero-order...?

Question

decomposition of ammonia on tungsten,

NH3 -> 1/2 N2 + 3/2 H2

where the rate constant is 2.08 x 10^-4 mol/L*s


I would appreciate any help with understanding this question, I am basically an idiot when it comes to higher level chemistry problems so I can't understand complex formulas without all the variables explained...

Answer 1

haha man I had my chem final last saturday, the profs killed us on it, it wasss brutal

but anyway

i would use this equation for a zero order:

[A] = -aKt + [Aintial]

[ ] brackets obviously concentration

Answer 2

Zero order means the rate doesn't depend on how much stuff you've got.

You are told that you lose 2.08 x 10^-4 M every second. You just need to work out how long it will take you at this rate to go from 1.25M to 0.388 M.

Try to understand the concepts and definitions, and I predict that your difficulty in assigning values to variables will evaporate.