5 moles of `SO_(2)` and 5 moles of `O_(2)` are allowed to react to form `SO_(3)` in a closed vessel. At the equilibrium stage 60% of `SO_(2)` is used up. The total number of moles of `SO_(2), O_(2) and SO_(3)` in the vessel now is

Options

A. 10.5
B. 3.9
C. `10.0`
D. 8.5

Answer

D

Explanation

`{(2SO_(2),+,O_(2),hArr,2SO_(3)),("Initially" rarr 5 "mole",,"5 mole",,"0 mole"),(" At eq" rarr 5(1-0.6),,5(1-0.3),,5 xx 0.6),("mole",,"Mole",,"Mole"):}`
When 60% `SO_(2)` is used up, the `O_(2)` used up = 30% & `SO_(3)` formed is 60% of initial amount of `SO_(2) rArr` Total no. of mole `=2 + 3.5 + 3 = 8.5`