417 x (29.03/25.42) = 476
476/235 = 2.02 rounds to 2 as a whole number so there are 2 of those groups present.
1. An organic compound with a formula mass of 417 g/mol was
analyzed for ethoxyl (CH3CH2O—) groups by the reactions
ROCH2CH3 + HI ROH + CH3CH2I
CH3CH2I + Ag+ + OH- AgI(s) + CH3CH2OH
A 25.42-mg sample of compound produced 29.03 mg of AgI. Howmany ethoxyl groups are there in each molecule?
2 answers
There is an easier way to do this, at least easier to understand I think. As follows:
mmols AgI = mg AgI/molar mass AgI = 29.03/235 = 0.124
You get 1 mmol AgI for every mmol of the CH3CH2O group. so you have 0.124 mmols of the ethoxy group.
molar mass of the group is 25.42/0.124 = about 205 so now
417/205 = 2.02 which rounds to 2 groups.
mmols AgI = mg AgI/molar mass AgI = 29.03/235 = 0.124
You get 1 mmol AgI for every mmol of the CH3CH2O group. so you have 0.124 mmols of the ethoxy group.
molar mass of the group is 25.42/0.124 = about 205 so now
417/205 = 2.02 which rounds to 2 groups.
1 answer