A certain substane A .Is mixed with an equal amountof a substance, B . At theend of 1.0 hr, A is 70% reacted . Howmuch will it be leftunreacted at the end of 2.5 hr,reaction with respect to Aof firstorder ?

A certain substane A .Is mixed with an equal amountof a substance, B .

1.	A certain substane A .Is mixed with an equal amountof a substance, B . At theend of 1.0 hr, A is 70% reacted . Howmuch will it be leftunreacted at the end of 2.5 hr,reaction with respect to Aof firstorder ?
Answer» `10%` `5%` `3%` `1%` SOLUTION :`k = (2.303)/t log [A]_(0)/[A]_(n) = ( 2.303)/(1.0) log (100)/30 ` Again ,` k = (2.303)/(2.5)log (100)/x` Hence, ` (2.303)/(1.0) log (100)/30= (2.303)/(2.5) log 100/x` ` log 100/x = 2.5 log (100)/30` ` log 100/x = 2.5( log100- log 30) ` ` 2.5XX 0.5220 = 1.307 ` ` 100/x= " antilog 1.307 or 100/x = 20.28` ` orx= 100/(20.28)= 4.93% = 5%` DENSITY of FEO =4 g/cc mass of1 unit cell = ` 1.25 xx 10^(-22) xx4 = 5 xx 10^(-22) g ` Mass of 1 molecule`= 72/ ( 6.023 xx 10^(23)) = 1.195 xx 10^(-22) g ` Hence, number of FeO moleculesper unitcell ` (5xx 10^(-22))/(1.195 xx10^(-22)) = 4.18 = 4 ` Hence,there are four` FE^(2+)`and four ` O^(2-)`ionsin each unitcell.