A30.7 g sample of strontium nitrate, sr(no3)2•nh2o, is heated to a constant mass of 22.9 g. calculate the hydration number.
im confused

Explanation:

1) Mass of water in the hydrated compound

Mass of water = Mass of the hydrated sample - mass of the dehydrated compound

Mass of water = 30.7 g - 22.9 g = 7.8 g

2) Number of moles of water

3) Number of moles of Strontium nitrate dehydrated, Sr (NO₃)₂

4) Ratio

Which means that the hydration number is 4.

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.

4d^55s^1 ( third choice)