Find the number of formula units in 50g sample of Ca(OH)2. Also find the number of moles
The formula unit is the lowest whole number ratio of ions of an ionic compound. In the case of Ca(OH)2, there is one Ca2+ ion and 2 (OH)- ions. It is not possible to reduce the ratio of the two ions to a simpler form.
The molar mass of Ca(OH)2 is approximately 74 g/mole. 50 grams of Ca(OH)2 is equivalent to 50/74 = 0.67 mole. The number of particles in one mole is equal to 6.02*10^23. This gives the number of formula units in 0.67 moles as 4.067*10^23.