100g of Ca3(po4)is how many moles​

How might this scientific phenomena be explained? a paper clip floats on water.

Which statement is true regarding the diagram of circle p? the sum of y and z must be 2x. the sum of y and z must be x. the difference of z and y must be 2x. the difference of z and y must be x

Ahelium balloon contains 16.9 l of helium at stp. how many atoms of helium are in the balloon