[neon flash!]

hi anyone able to help me with some kinetics questions.

q1) What are the units of the rate constant if the rate equation states: rate = k [A]1/2?

as far as i know
Order             Units
0                     mol L-1 s-1
1                     s-1
2                     L mol-1 s-1
the overall rxn order for this should be 1+1/2 (coz you add the powers) which is 3/2 but i don tknow what units this matches!?

Q2) Define the term “primary quantum yield”.
i dont even know what context this is referring to


Q3)  At 400 K, the half life for the decomposition of a sample of a gaseous compound initially at 55.5 kPa was 340 s. When the pressure was 28.9 kPa, the half-life was 178s. Determine the order of reaction.
i looked at botht eh equations (1st and 2nd order) for half life but i need to know my k value in order to use them (which i dont) so i assume i must do something else?