A gaseous `A_(2)(g) rarr B(g) +(1)/(2) C(g)`, shows increase in pressure from 100 mm to 120 mm in 5 min. The rate of disappearance of `A_(2)` is

Options

A. 4 mm `"min"^(-1)`
B. 8 mm `"min"^(-1)`
C. 16 mm `"min"^(-1)`
D. 2 mm `"min"^(-1)`

Answer

B

Explanation

`{:(,A_(2)(g)rarr,B(g)+,(1)/(2)C(g)),("Initially",100mm,0,0),("After 5min",(100-p)min,p,(1)/(2)p):}`
Total pressure = `100 - p + p +(1)/(2) p = 100 +(1)/(2) p`
`therefore` Increase in pressure =` (1)/(2) p = 120 - 100 = 20 mm`
`therefore` Decrease in pressure of `A_(2) = 2 xx 20 = 40 mm`
`therefore` Rate of disappearance of `A_(2)=(dx)/(dt)=(40)/(5)=8 mm " min"^(-1)`