The empirical formula for biomass of an unknown organism

Home » Biochemical » Biochemical Miscellaneous » Question

The empirical formula for biomass of an unknown organism is CH_1.8 O_0.5 N_0.2. To grow this organism, ethanol (C₂H₅OH) and ammonia are used as carbon and nitrogen sources, respectively. Assume no product formation other than biomass. To produce 1 mole of biomass from 1 mole of ethanol, the number of moles of oxygen required will be ___________.

1. 1.9 to 2.0
2. 5.9 to 7.2
3. 1.0 to 1.5
4. None of the above

Correct Option: A

The equation for biomass production is

Now making elemental balance on both sides.
LHS C = 2
N = a i.e. a = 0.2
RHS C =1 + d = 2 i.e. d = 1
N = 0.2
Now, putting value of a & d in equation (i)

Now, H balance
LHS H = 6 + 0.6 = 6.6
RHS H = 1.8 + 2e = 6.6
∴ e = 2.4
and finally O₂ balance
LHS
0 = 1 + 2b
RHS
0 = 0.5 + 2 + 2.4 (i.e. e = 2.4) = 4.9
hence1 + 2b = 4.9
∴ 2b = 3.9
∴ b =1.95
∴ Final equation
C₂H₅OH + 0.2 NH₃ + 1.95O₂ → CH_1.2O_0.5N_0.2 + CO₂ + 2.4 H₂O