A 2.00 liter evacuated container has a mass of 1050.0 g. When the container is filled with an unknown gas at 800. mm Hg pressure and 25.0 °C the mass is 1052.4 g. What is the molar mass of the gas (in g-mol"')? (A) 28
(B) 31
(C) 54
(D) 56

(A) 28

Explanation:

To solve this problem we use the PV=nRT equation, where:

We input the data:

And solve for n:

Now we calculate the gas' mass:

Finally we calculate the unknown gas' molar mass, using its mass and its number of moles:

So the answer is option (A).

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.