Chapter 8 - Electron Configurations and Periodicity - Questions and Problems - Page 333: 8.112

$0.5384 g $

We know that $n=\frac{PV}{RT}$ We plug in the known values to obtain: $n=\frac{\frac{768}{760}\times 0.0481}{0.082057\times 292.2}=0.002027 mol \space H_2$ $mol \space Cs=0.002027\times \frac{2\space mol Cs}{1 mol\space H_2}=0.004054 mol \space Cs$ Now mass of Cs $0.004054\times \frac{132.9}{1 \space mol \space Cs}=0.5384 g $