Amatch has about 21 milligrams of red phosphorus coating the tip. how many atoms of phosphorus is this?

4.083 * 10^20 atoms.

Explanation:

One Mole of phosphorus  contains 6.022 * 10^23 atoms (Avogadros number)'

Since 1 mole of Phosphorus  has a mass of  30.974 grams, 21 milligrams has

6.022 * 10^23  * 0.021 / 30.974

= 0.004083 * 10^23

= 4.083 * 10^20

b) mutualism

hope this : )

water at room temperature is flowing through a pipe with pressure taps located 10 ft apart along one section of the pipe, which are connected to a mercury (s=13.6) manometer.