Verified Solution • 2025–26 Session moderate

QJEEM20Chf535: JEE Main 2020 Chemistry - Class 11 JEEM20Chf535 Solution: A soft drink was bottled with a partial pressure of CO 2 of 3…

A soft drink was bottled with a partial pressure of CO2 of 3 bar over the liquid at room temperature. The partial pressure of CO2 over the solution approaches a value of 30 bar when 44 g of CO2 is dissolved in 1 kg of water at room temperature. The approximate pH of the soft drink is ______ ×\times 10–1.
(First dissociation constant of
H2CO3 = 4.0 ×\times 10–7; log 2 = 0.3; density
of the soft drink = 1 g mL–1) .

Step-by-Step Verified Solution

CO2 + H2O →\to H2CO3

At 30 bar pressure mass of CO2 in 1 kg water = 44 gm

At 3 bar pressure mass of CO2 in 1 kg water = 4.4 gm

∴\therefore Moles of CO2 in 1 kg water = 4.444{{4.4} \over {44}} = 0.1

H2CO3 ⇌ H+ + HCO3-
t = 0 0.1 0 0
t = teq 0.1(1 - α\alpha ) 0.1 α\alpha 0.1 α\alpha


4.0 ×\times 10–7 = 0.1α21−α{{0.1{\alpha ^2}} \over {1 - \alpha }}

1−α{1 - \alpha } ≃\simeq 1

⇒\Rightarrow 0.1 α2{{\alpha ^2}} = 4 ×\times 10-7

⇒\Rightarrow α\alpha = 2 ×\times 10-3

[H+] = 0.1 α\alpha = 2 ×\times 10-4

∴\therefore pH = –[– 4 × log(2)] = 3.7 = 37 × 10–1

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