Can someone explain how to do 5 & 6?

Determine the number o moles of ions/atoms/particle in the following: 2.50 miles of k2s (let me know how to do)

To save time, you can approximate the initial mass of the solid to the nearest ±1 g. for example, if you are asked to add 14.3 g of copper, add between 13 g and 15 g. which of the following sets include two samples with an equal density? which all that apply below 15.4 g gold and 18.7 g silver 15.2 g copper and 50.0 g copper 20.2 g silver and 20.2 g copper 11.2 g gold and 14.9 g gold

How manyatoms of mercury are in 1.4214e+1 ml sample