At 373 k, the following reaction `A(g)rarr2B(g)+C(g)` is found to be of first order. Starting with pure A, the total pressure at the end of 10 minutes was 176 mm Hg and after a long time when A was completely dissociated, it was 270 mm Hf. The pressure of A at the end of 10 minutes was

Options

A. 94 mm Hg
B. 47 mm Hg
C. 43 mm Hg
D. 90 mm Hg

Answer

B

Explanation

`{:(A(g),overset(Delta)(rarr),2B(g),+,C(g)),(P,,0,0,"(Initial)"),(P-p,,2p,p,"(After 10 min)"),(0,,2P,P,"(After long time)"):}`
Total pressure after 10 min
`= P-p+2p+p=P+2p`
`P+2p=176` mm Hg
Total pressure after long time `= 3P = 270` mm Hg
`:. P=90` mm Hg
`p=(176-P)/(2)"mm Hg"=(176-90)/(2)"mm Hg"`
=43 mm hg
Pressure of A after 10 minutes
`=P-p=90 - 43 = 47` mm Hg.