3) Carbonated beverages such as soda, beer, or sparkling water are produced by d

Question

3) Carbonated beverages such as soda, beer, or sparkling water are produced by dissolving CO2 in

the aqueous beverage: CO2(g) CO2(aq)

a. Calculate G° of dissolution for CO2. Is it spontaneous under standard conditions?

b. What is the equilibrium constant at 25°C for the dissolution of CO2?

c. To achieve carbonation of 2.5 volumes in a drink (equivalent to 0.10 M concentration of dissolved CO2) at 25°C, what pressure of CO2 gas is required?

d. What pressure of CO2 gas is required to achieve the same carbonation at 4°C?

Explanation / Answer

(a)

G° = G°f(CO2,aq.) - G°f(CO2,g)

= - 386.2 - ( - 394.4 )

= + 8.2 kJ

Since G° = +ve the reaction is not spantaneous under standard conditions.

(b)

G°= - R T lnK

8.2 = - 0.008314 * 298 * lnK

lnK = - 3.31

K = 0.0365

(c) Assuming ideal behavior of CO2,

P V = n R T
P = (n/V) R T

P = C R T
P = 0.10 * 0.0821 * 298

P = 2.45 atm

(d)

P = C R T

P = 0.10 * 0.0821 * 277

P = 2.27 atm

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