The question requires us to calculate the amount of moles of Ca(OH)2 contained in 188g of this compound.
To answer this question, first we need to calculate the molar mass of Ca(OH)2 and then convert the mass given (188g) into moles.
The atomic masses of calcium (Ca), oxygen (O) and hydrogen (H) are as follows:
Ca: 40.08 u
O: 15.99 u
H: 1.00 u
Next, we calculate the molar mass of Ca(OH)2 considering the atomic mass of its elements and the amount of atoms of each element (remember that when we have a parenthesis in the chemical formula, we should multiply the number outside of the parenthesis by each number inside of them):
molar mass Ca(OH)2 = (1 * 40.08) + (2 * 15.99) + (2 * 1.00) = 74.06 g/mol
Now we know that for each 74.06 g of Ca(OH)2, there is 1 mol of this compound.
Next, we calculate the amount of moles in 188g of Ca(OH)2:
74.06 g --------------- 1 mol
188 g ------------------ x
Solving for x:
x = [(188 g) * (1 mol)] / (74.06 g) = 2.54 mol
Therefore, there are 2.54 moles of Ca(OH)2 in 188g of this compound.