How many molecules are in 2.50 moles of 02

1.5 × 1024  molecules

Explanation:

You can calculate the number of molecules from moles by using Avogadro's constant,

6.02×1023 molecules

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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.