Answer: Partial pressure of CO in the sealed vessel is 0.47 atm.
Explanation: From Dalton's law of partial pressures, "Total pressure is the sum of partial pressures of the gases present in the mixture."
So, total pressure = partial pressure of carbon monoxide + partial pressure of oxygen + partial pressure of carbon dioxide
Let's plug in the values in the formula:
2.68 atm = partial pressure of CO + 1.56 atm + 0.65 atm
2.68 atm = partial pressure of CO + 2.21 atm
partial pressure of CO = 2.68 atm - 2.21 atm
partial pressure of CO = 0.47 atm
Hence, the partial pressure of carbon monoxide gas in a sealed vessel is 0.47 atm.