Aballoon with a volume of 8.00 l is known to contain 1.200 moles of gas. how many moles of gas remain if some of the gas is released and the new volume is 5.25 l. assume temperature and pressure remain constant

Avagadros law states that at constant pressure and temperature conditions the volume is directly proportional to number of moles of gas

where v1 is volume and n1 is number of moles at first instance

v2 is volume and n2 is number of moles after some of the gas is released

substituting the values in the equation

n2 = 0.788 mol

after some of the gas is released only 0.788 mol remain

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.