Question

In a laparoscopic surgical procedure, the insufflator pumps a mixture of 95.00 %(w/w) of CO2 (insufflating gas) and 5.00 %(w/w) of N2O (anesthetic agent) at 37 °C in the abdominal cavity until the intra-abdominal pressure reaches 1.500 ´ 10−2 atm. Calculate the partial pressures of CO2 (Mr = 44.01) and N2O (Mr = 44.01) in the mixture

Answer 1

First calculate the mole fraction of CO2 and N2OO

Consider 100g of mixture

Mass of CO2 = 95g

Molar mass of CO2 = 44.01g/mol

No of mole of CO2 = 95g/44.01g/mol = 2.1586

Mass of N2O = 5g

Molar mass of N2O = 44.01g/mol

No of mole of N2O = 5g/44.01g/mol = 0.1136

Total No of mole = 2.1586 + 0.1136 = 2.2722

Mole fraction of CO2 = 2.1586/2.2722=0.9500

Mole fraction of N2O = 0.1136/2.2722= 0.0500

Total pressure at intra -abdomen = 1.5×10^-2atm

Partial pressure = mole fraction × total pressure

Therefore,

Partial pressure of CO2 = 0.95×1.5×10^-2atm =0.01425atm

Partial pressure of N2O = 0.05× 1.5×10^-2atm =0.00075atm