1.

Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law, with `t_(1//2)=3.00hr.` What fraction of sample of sucrose remains after `8 hr` ?

Answer» For a first order reaction ,
`k = (2.303)/(t) "log" ([R]_(0))/([R])`
It is given , `t_(1//2) = 3.00` hours
`k = (0.693)/(t_((1)/(2)))`
Therefore ,
= `(0.693)/(3) h^(-1)`
= `0.231 h^(-1)`
Then , `0.231 h^(-1) = (2.303)/(8h) "log" ([R]_(0))/([R])`
`implies "log" ([R]_(0))/([R]) = (0.231 h^(-1) xx 8 h)/(2.303)`
`implies ([R]_(0))/([R])`= antilog (`0.8024`)
`implies ([R]_(0))/([R]) = 6.3445`
`implies ([R])/([R]_(0)) = 0.1576` (approx)
=`0.158`
Hence , the fraction of sample of sucrose that remains after 8 hours is `0.158`


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