explain how you would make 200. mL of a 0.150 M solution of calcium chloride, if provided with the solid
First we get the amount (the mass, specifically) of calcium chloride needed. Mass is related to number of moles.
Recall that molarity (M) is just number of moles (n) divided by the volume (V) in liters:
M = n/V
Therefore,
n = MV
n = (0.15 M)(0.2 L)
n = 0.03 moles
Now, to get the mass, we multiply n by the molar mass of CaCl2. To get the molar mass, get a periodic table & just add the individual masses of the elements in the chemical formula:
CaCl2: 1*40 + 2*35.45 = 110.9 g/mol
Thus the mass is
0.03 mol * 110.9 g/mol = 3.33 g CaCl2
For the general steps:
*Weigh 3.33 grams of Calcium Chloride and put it in a container (for instance, in a 250-mL beaker)
*Add 200 mL of H2O and stir.
(Of course, laboratory steps/instructions are different and more precise) ;)
hope this helps~ :3