A reaction $X_{2_{\left(g\right)}}\to Z\left(g\right)+\frac{1}{2}{Y}_{\left(g\right)}$ exhibits an increase in pressure from 150 torr to 170 torr in 10 min. What is the average rate of formation of $Y_2$ in 10 min? Report your value in torr per min.

 $X_{2\left(g\right)}\to Z_{\left(g\right)}+\frac{1}{2}{Y}_{\left(g\right)}$
t = 0 150        0        0
$t=10\min 150-xx\frac{x}{2}$ 
Total pressure = $150-x+x+\frac{x}{2}$  
$170=150+\frac{x}{2}$ 
x = 40 mm
Rate of disappearance of $x_2=\frac{40}{10}=4mm/Min$  
Rate of disappearance of $X_2=\frac{1}{2}$ rate of appearance of Y