how to prepare approximately 100 ml of a .12M copper (II) chloride solution using a 50.5% by mass copper (II) chloride that has a density of 1.05 g/ml

50.5% by mass means 50.5 g CuCl2/100 g soln.

Convert that to molarity, then use the dilution formula of
mL x M = mL x M.

To prepare approximately 100 ml of a 0.12M copper (II) chloride solution using a 50.5% by mass copper (II) chloride with a density of 1.05 g/ml, we need to follow these steps:

Step 1: Calculate the required moles of copper (II) chloride:
First, we need to determine the number of moles of copper (II) chloride required to make the desired concentration. The molarity (M) of a solution is defined as moles of solute per liter of solution. In this case, we want a 0.12M solution, so we need to calculate the moles using the formula:
moles = Molarity × Volume (in liters)

Given that you need approximately 100 ml of the solution, we need to convert it to liters by dividing it by 1000 ml/L:
Volume (in liters) = 100 ml ÷ 1000 ml/L = 0.1 L

Now we can calculate the required moles:
moles = 0.12 M × 0.1 L = 0.012 moles

Step 2: Calculate the mass of copper (II) chloride required:
To calculate the mass of copper (II) chloride required, we need to know the molar mass of copper (II) chloride. The molar mass of copper (II) chloride is the sum of the atomic masses of copper (Cu) and chlorine (Cl), taking into account the number of atoms of each element in the formula. Copper has an atomic mass of 63.55 g/mol, and chlorine has an atomic mass of 35.45 g/mol. The formula for copper (II) chloride is CuCl2, so the molar mass is:
molar mass = (atomic mass of Cu × 1) + (atomic mass of Cl × 2)
molar mass = (63.55 g/mol × 1) + (35.45 g/mol × 2)
molar mass = 63.55 g/mol + 70.90 g/mol
molar mass = 134.45 g/mol

Now we can calculate the mass of copper (II) chloride required using the formula:
mass = moles × molar mass
mass = 0.012 moles × 134.45 g/mol
mass = 1.6134 g

Step 3: Calculate the volume of copper (II) chloride required:
To calculate the volume of copper (II) chloride required, we need to use its density. Density is defined as mass per unit volume. In this case, the density of copper (II) chloride is provided as 1.05 g/ml. We already calculated the mass required in Step 2, which is 1.6134 g. Now we can use the formula:
volume = mass ÷ density
volume = 1.6134 g ÷ 1.05 g/ml
volume = 1.537 ml

Step 4: Dilute the copper (II) chloride solution:
Since we obtained a volume of 1.537 ml from the previous step, we need to dilute it to achieve the desired volume of approximately 100 ml. You can use a graduated cylinder or a volumetric flask to measure accurately. Add the calculated volume of copper (II) chloride solution (1.537 ml) to the flask and then add the necessary amount of solvent (e.g., water) to reach the final volume of approximately 100 ml. Be sure to mix the solution thoroughly.

Note: To ensure accuracy, it is always a good idea to use precise measuring utensils and follow proper lab techniques.