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

A

Explanation

`{:(,2SO_(2),+,O_(2),hArr,2SO_(3)),("Initil moles",4,,4,,0),("Moles at eqm.",4(1-0.25),,4(1-0.25),,0.25xx2):}`
Total number of moles
`=4(1-0.25)+4(1-0.25)+0.5`
`=4-1+4-1+0.5=6.5`