Final answer:
In a mercury manometer, the pressure of the gas can be determined by measuring the height difference of the mercury columns in the two arms of the U-tube. For an open-end manometer, the gas pressure is equal to the difference in the height of the mercury columns in the arm connected to the gas and the height of the mercury column in the arm open to the atmosphere. Given that the atmospheric pressure is 760 mmHg, the pressure of the gas can be calculated by subtracting the height of the mercury column in the open arm from 760 mmHg.
Step-by-step explanation:
In a mercury manometer, the pressure of the gas can be determined by measuring the height difference of the mercury columns in the two arms of the U-tube.
For an open-end manometer, the gas pressure is equal to the difference in the height of the mercury column in the arm connected to the gas and the height of the mercury column in the arm open to the atmosphere.
Given that the atmospheric pressure is 760 mmHg, the pressure of the gas can be calculated by subtracting the height of the mercury column in the open arm from 760 mmHg.
So, if the pressure of the atmosphere is 0.990 atm, then the pressure of the gas in mmHg would be 0.990 * 760 mmHg = 752.4 mmHg.