Answer:
To make a 1 M solution of CaCl2, you need to dilute the stock solution of 3.2 M CaCl2. The equation to use is:
C1V1 = C2V2
where C1 is the concentration of the stock solution (3.2 M), V1 is the volume of the stock solution used, C2 is the concentration of the desired solution (1 M), and V2 is the final volume of the desired solution.
To calculate how much of the stock solution you need to use, you rearrange the equation to get:
V1 = (C2 x V2) / C1
Substituting the values given, we get:
V1 = (1 M x 900 ml) / 3.2 M
V1 = 253.125 ml
Therefore, to make a 1 M solution of CaCl2, you need to measure 253.125 ml of the 3.2 M stock solution and add enough water to make the final volume up to 900 ml.