UPSEE Solved Model Paper 7

Given:
Empirical formula of a non-electrolyte = CH2O
Mass of compound taken = 6 g
Concentration of glucose solution = 0.05 M
(Osmotic‌pressure)compound = (Osmotic‌pressure)glucose
We have to find !tie molecular formula of the compound
Now, the empirical formu!a mass of CH2O is:
= 12 + 2 × 1 + 16 = 30
Let molar mass of the compound be 'M'.
Let osmotic pressure of the compound and glucose be π1 and π2 respectively and as given:
(Osmotic‌pressure)compound = (Osmotic‌pressure)glucose
or,
π1 = π2
Thus,
C1RT = C2RT
or,
C1 = C2 ... (i)
where, C1 = Concentration of solution of compound
C2 = Concentration of glucose solution
R = Gas constant
T = Temperature
Now, molarity is given by:
Molarity =

Number‌of‌moles

Volume‌of‌solution(in‌L)

Number of moles is given by :
Mole =

Mass

Molecular‌mass

Thus,
C1 =

6

M

From equation (i) , we get

6

M

= 0.05
M =

6

0.05

= 120
Now,
n =

Molecular‌mass

Empirical‌formula‌mass

... (ii)
where, n = Simple whole number
Substituting the values in equation (ii). we get
n =

120

30

= 4
Therefore, molecular formula of the compound = (CH2O)n
= (CH2O)4
= C4H8O4
Hence, option 'D' is correct.