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We discuss the dependence of various properties of the star formation rate(SFR) and efficiency (SFE) in molecular clouds (MCs) on the maximum massreached by the clouds, based on a previously-published model for MC and SFRevolution in which the clouds were assumed to be undergoing global collapse,and the SFR was controlled by ioniztion feedback. Because the model neglectsvarious other processes, the results presented are upper limits. We find thatclouds with $\Mmax \lesssim 10^4 \Msun$ end their lives with a mini-burst, atwhich the SFR reaches a peak of $\sim 10^4 ~\Msun \Myr^{-1}$, although its timeaverage is only $\SFRavg \sim \hbox{ a few} \times 10^2 \Msun \Myr^{-1}$. Thecorresponding efficiencies are $\SFEmax \lesssim $60\%$ and $\SFEavg \lesssim$1\%$. For more massive clouds ($\Mmax \gtrsim 10^5 ~ \Msun$), the SFR firstincreases and then remains roughly constant for $\sim 10^7$ yr, because theclouds are influenced by the stellar feedback since earlier in their evolution.We find that $\SFRavg$ and $\SFEavg$ are well represented by the fits $\SFRavg\approx 100 (1+\Mmax/2 \times 10^5 ~ \Msun)^{2} ~ \Msun \Myr^{-1}$ and $\SFEavg\approx 0.024 (\Mmax/10^5 ~ \Msun)^{0.28}$, respectively. The massive modelclouds follow the SFR-dense gas mass relation obtained by Gao \& Solomon forinfrared galaxies, extrapolated down to MCs scales. Low-mass clouds fall abovethis relation, in agreement with recent observations. An integration of themodel-predicted $\SFRavg$ over a Galactic GMC mass spectrum yields a realisticvalue for the Galactic SFR. Our results reinforce the suggestion thatstar-forming GMCs may be in global collapse, and still have low net SFRs andSFEs, due to the evaporation of most of the cloud material by the feedback frommassive stars.

An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity. II. Mass Dependence of the Star Formation Rate