1.

Some solid NH_(4) HS " is placed in a flask containing " NH_(3) " at " 0*5 " atm. What would be the pressure of " NH_(3) and H_(2)S " when equilibrium is reached " ? NH_(4) HS (s) hArr NH_(3) (g) + H_(2) S (g), K_(p) = 0*11

Answer»

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Solution :`NH_(3) and H_(2)S ` PRODUCED by the decomposition of `NH_(4)HS`will be same . Suppose at equilibrium each has pressure= p atm due to decompistion of ` NH_(4)HS` . Then
` p_(H_(2)S) = p atm `
` p_(NH_(3) ) p + 0*5" "(:' NH_(3) " is already presentat" 0*5atm )`
Applying law of chemical equilibrium to the given reaction
`p_(NH_(3)) xx p_(H_(2)S) = K_(p)`
`:.p xx(p + 0*5)= 0*11`
or ` p^(2) + 0*5 p = 0*11`
or`p^(2) + 0*5 p - 0*11 = 0 `
` :. p= -0*5pm sqrt((0*5)^(2)-4 (-0*11))/2 = (0*5 pm sqrt (0*25 + 0*44))/2= -(0*5 pm sqrt(0*69))/2`
` ( -0*5 pm 0*83 )/2 = (0*33)/2 = 0*165 ("Neglecting-ve value ")`
` :. p_(H_(2)S) = 0* 165 "atm " , p_(NH_(3))= 0*665 " atm "`


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