A flask containing helium gas is connected to an open-ended mercury manometer. The open end is exposed to the atmosphere, where the prevailing pressure is 752 torr. The mercury level in the open arm is 47 mm above that in the arm connected to the flask of helium. What is the helium pressure, in torr?

The helium pressure is 799 torr.

Explanation:

It is known that 1 mm Hg is equal to 1 torr. As we are given an open-ended mercury manometer so, its pressure will also be equal to the atmospheric pressure which is given as 752 torr.

And, it is given that pressure of mercury level in the open arm is 47 mm above that in the arm connected to the flask of helium. Therefore, adding both the pressures we will get the pressure of helium as follows.

                (752 + 47) mm Hg

              = 799 mm Hg

or,           = 799 torr

Thus, we can conclude that the helium pressure is 799 torr.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms