How do you do this problem?
Calcuate the mass of CuCl2*5H2O required for preparing 400mL solution that of .25M in chloride ions.
How many mols Cl^- do you want? M x L = mols.
Since there are two Cl atoms in 1 molecule of CuCl2.5H2O, you need 1/2 that of CuCl2.5H2O.
Then mols = grams/molar mass. You know molar mass and you know mols, solve for grams.
To calculate the mass of CuCl2*5H2O required for preparing a 400 mL solution that is 0.25 M in chloride ions, we need to follow these steps:
Step 1: Determine the molar mass of CuCl2*5H2O.
The molar mass of CuCl2 can be found by adding up the atomic masses of its constituent elements: Cu (copper) has a molar mass of 63.55 g/mol, Cl (chlorine) has a molar mass of 35.45 g/mol, and H2O (water) has a molar mass of 18.02 g/mol. Since there are two chlorine atoms in CuCl2, we multiply the molar mass of Cl by 2.
Molar mass of CuCl2 = 63.55 g/mol + (35.45 g/mol * 2) = 134.45 g/mol
Hence, the molar mass of CuCl2*5H2O can be calculated using the above-mentioned molar mass of CuCl2 and by adding the molar mass of five water molecules (5 * 18.02 g/mol).
Molar mass of CuCl2*5H2O = (134.45 g/mol) + (5 * 18.02 g/mol) = 249.55 g/mol
Step 2: Calculate the moles of chloride ions required in the solution.
We want a solution that is 0.25 M in chloride ions. Molarity (M) is defined as moles of solute per liter of solution. Since our desired solution volume is 400 mL (0.4 L), we can calculate the number of moles of chloride ions needed using the formula:
Moles of chloride ions = Molarity * Volume
Moles of chloride ions = 0.25 mol/L * 0.4 L = 0.1 mol
Step 3: Determine the mass of CuCl2*5H2O required.
To calculate the mass of CuCl2*5H2O required, we can multiply the moles of chloride ions (calculated in the previous step) by the molar mass of CuCl2*5H2O:
Mass = Moles * Molar mass
Mass = 0.1 mol * 249.55 g/mol
Mass ≈ 24.96 grams
Therefore, approximately 24.96 grams of CuCl2*5H2O are required to prepare a 400 mL solution that is 0.25 M in chloride ions.