Question

How many moles of Ca(OH)2 are in 3.5kg of Ca(OH)2? Answer in units of mole

Answer 1

First, you need to convert kg to g. 
So, 1 kg =1000g.
3.5 x 1000 = 3500g Ca(OH)2

We need to know the molar mass of Ca(OH)2. 
Ca= 40.08 g
O=2(15.999)
H=2(1.0079)

Add them all together and you get 74.0938 g.

Put it in the formula from mass to moles. 

# of moles = grams Ca(OH)2 x 1 mol Ca(OH)2
                                                  --------------------
                                                  molar mass Ca(OH)2

3500 g Ca(OH)2 x 1 mol Ca(OH)2
                              ---------------------
                             74.0938 g Ca(OH)2

So divide 1/74.0938 and multiply by 3500.

You will get about 47.24 moles Ca(OH)2.

Hope this helps! :)

Answer 2

Answer:

47.3 moles of $Ca(OH)_2$ are in 3.5 kilograms of $Ca(OH)_2$.

Explanation:

$n=\frac{m}{M}$

Where:

n =  Moles of the compound

m=  Given mass of the compound

M =  Molar mass of the compound

Mass of the calcium hydroxide, m = 3.5 kg = 3500 g (1kg = 1000 g)

Molar mass of the calcium hydroxide = M = 74 g/mol

Moles of calcium hydroxide = n

$n=\frac{3500 g}{74 g/mol}=47.297 mol\approx 47.3 mol$

47.3 moles of $Ca(OH)_2$ are in 3.5 kilograms of $Ca(OH)_2$.