Answer:0.59ATM
Explanation:The total pressure of a mixture of gases is the sum of the partial pressures of the individual gases. In this case, the total pressure of the mixture of helium and neon is 726 torr + 726 torr = 1452 torr. Since the pressure gauge on the container measured a higher pressure than this, we can conclude that a third gas was added to the mixture.
The pressure of the third gas can be calculated by subtracting the total pressure of the helium and neon from the measured pressure of the mixture:
pressure of third gas = 1900 torr - 1452 torr = 448 torr
To convert this pressure to atmospheres, we need to know the conversion factor between torr and atm. One atmosphere is equivalent to 760 torr, so we can use this value to convert the pressure of the third gas to atmospms:
pressure of third gas in atm = 448 torr / 760 torr/atm = 0.59 atm
Thus, the third gas contributed a pressure of approximately 0.6 atm to the mixture. This answer is rounded to two significant figures, as required.