[Johnny010]

Hello there.

I am just going through some past exam questions and hit a problem:

Q:
A particular excited molecule can return to its ground state only by fluorescence
(k_fl = 1.0 × 10⁹ s^–1) or quenching (k_q = 1.5 × 10^–10 cm³ molecule^–1 s^–1). For a concentration of
quencher, Q, equal to 1.3 × 10¹⁹ molecule cm^–3, calculate the fraction of excited molecules
which fluoresce following their generation in a laser pulse.

A:
I have tried a few things with some equations I have written in my notes but can not seem to get this at all...please help  .

My attempt:
Rate of florescence=(k_f + k_q[Q])[S₁]  Where S₁ is the excited molecule concentration.

Rate of florescence=(1e⁹*1.95e⁹)[S₁]
Rate=


And I am just lost.