A thick coating of plaster of Paris is applied over the bandage on a fracture bone. It becomes hard on drying to keep the fractured bone immobilized. Can the change in POP be reversed? Identify the change?

The change in POP can not be reversed hence it is a chemical change.

Explanation:

Plaster of Paris (POP) is used to immobilize a fractured bone. The POP sets when water is added to it, it hardens irreversibly. Once it hardens, its shape can not be changed by any physical means. This means that the hardening of POP is a chemical change.

The chemical name of plaster of Paris is calcium sulfate hemihydrate. The setting of POP is an example of a chemical reaction.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.