4 moles each of `SO_(2) "and" O_(2)` gases are allowed to react to form `SO_(3)` in a closed vessel. At equilibrium 25% of `O_(2)` is used up. The total number of moles of all the gases at equilibrium is

Options

A. `6.5 `
B. `7.0`
C. `8.0`
D. `2.0`

Answer

B

Explanation

`2SO_(2) +O_(2) hArr 2SO_3`
`{:("Initial moles",4,4,0),("Final Moles." ,(4 – 2) ,(4 – 1) ,2),((25%O_2 "consumed") ,"=2","=3","=2"):}`
Total number of moles = 2 + 3 + 2 = 7.