What is the mass of 0.25mol of NO3- ions/nitrate ions

15.5 grams

Explanation:

molar mass of NO3=62g/moles

number of moles=0.25mol

mass in gram= ?

as we know that

number of moles=

number of moles×molar mass=mass in grams

mass in grams=62g/moles×0.25moles

mass in grams=15.5grams

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.