X

Structural Formula Part-1

Structural Formula-

source : chem collective.org

Structural Formula-

Q 1– Two isomeric compounds ( A) & (B) have C =52.17 %; H =13.04 % & rest is oxygen.Their vapour density is 23.

Compound ‘A’ on reaction with HI gives a compound  ‘C’ which when reacted with aq . NaOH  gives C2H5OH . Explain the  reactions.Identify A , B & C.Give their name & formula

Solution-

percentage of C= 52.17% ; % of H= 13.04 %

% of O = 100–(52.17+13.04)= 34.79 %

 

Element % Atomic weight Relative no. of atoms Simplest Ratio
C 52.17 12 52.17/12= 4.35 4.35/2.17 =2
H 13.04 1 13.04/1 = 13.04 13.04/2.17=6
 O  34.79  16  34.79/16=2.17  2.17/2.17=1

Empirical formula =C2H6O

mol.formula=(C2H6O)n

Empirical formula weight =12 x 2+6 x 1+16 =46

mol. wt. = 2 x V.D =2 x 23=46

n = mol.wt. /Empirical formula weight

=46/46=1

n =1

mol.formula = (C2H6O)n

mol.formula = (C2H6O)1 =C2H6O

The possible isomers of C2H6O are, C2H5OH & CH3OCH3

Compound A is ethanol  because it on reaction with HI gives’ C’ i.e C2H5I . Compd ‘C’ on hydrolysis with aq.NaOH gives ethyl alcohol.

 

C2H5 I + NaOH(aq.)—–>C2H5OH +NaI

compound A is C2H5OH(Ethyl alcohol) ; compound B is CH3OCH3 (dimethyl ether) ; compound C is C2H5I(Ethyl iodide).


Q 2– Molecular formula of compd ‘A’ & ‘B’ is CH2O & C2H4O2 respectively . ‘A’ reduces ammonical AgNO3 solution but ‘B’ does not.The neutral solution of ‘B’ gives a red colour with neutral FeCl3.Find the  formula of  both compds & give their names?

Ans.

Molecular formula of A is CH2O.

Because it reduces  ammonical AgNO3 solution hence it is an aldehyde. Thus compd is HCHO.

So ‘A’ is HCHO ( formaldehyde).

Molecular formula of ‘B’ is C2H4O2.

Hence ‘B’ gives red colour with neutral FeCl3 hence it is an acid . Thus compd is CH3COOH.

So ‘B’ is CH3COOH ( acetic acid).


Q 3– Molecular formula of compd ‘A’ & ‘B’ is CH2O & C2H4O2 respectively . ‘A’ reduces fehling solution but does not react with Na2CO3 solution.   ‘B’ does not reduce fehling solution but gives effervesence  with Na2CO3.Find the   name & formula of  both compds?

Ans.

Molecular formula of A is CH2O.

Because it reduces fehling solution hence it is an aldehyde. Thus compd is HCHO.

So ‘A’ is HCHO ( formaldehyde).

Molecular formula of ‘B’ is C2H4O2.

As  we know that ‘B’ gives effervesence  with Na2CO3. An acid gives effervesence with Na2CO3 solution.  hence it is an acid . Thus compd is CH3COOH.

So ‘B’ is CH3COOH ( acetic acid).


Read more articles at chemistryonline.guru

Saroj Bhatia: Dr. Saroj Bhatia is an Ph.D in chemistry who has been teaching chemistry for over a decade. Currently she is a respected principal of a renowned college in her hometown. She took this medium for online users. Her proudest achievement is helping people learn chemistry.
Related Post