How do you find the number of grams of #CO_2# that exert a pressure of 785 mmHg at a volume of 325 L and a temperature of 32°C?
We know (or should know) that
From where did I get the figure
My own feeling is that you should never use a column of mercury to measure pressure ABOVE atmospheric pressure. You will end up getting mercury EVERYWHERE. A column of mercury is suitable for measuring LOW pressures. These days, mercury is rarely present in a laboratory due to safety concerns.