to make 100mL of a solution that is .25M in chloride ion, how many grams of MgCl2 would you need to dissolve
To calculate the number of grams of MgCl2 needed to make 100mL of a 0.25M chloride ion solution, we need to consider the molar mass of MgCl2 and the desired molarity.
Step 1: Determine the molar mass of MgCl2.
Mg has a molar mass of approximately 24.31 g/mol, and Cl has a molar mass of approximately 35.45 g/mol. Since there are two Cl atoms in MgCl2, we can calculate the molar mass as follows:
Mg: 1 atom * 24.31 g/mol = 24.31 g/mol
Cl: 2 atoms * 35.45 g/mol = 70.9 g/mol
Total molar mass of MgCl2 = 24.31 g/mol + 70.9 g/mol = 95.21 g/mol
Step 2: Calculate the number of moles of chloride ions needed.
Since we want a 0.25M chloride ion solution, we know that the concentration of Cl ions is equivalent to the concentration of MgCl2. Therefore, 0.25 moles of Cl ions are required in 1 liter (or 1000mL) of solution.
Number of moles of Cl ions = 0.25 moles/L
Step 3: Calculate the number of moles of MgCl2 required.
Since MgCl2 dissociates into one Mg2+ ion and two Cl- ions, the number of moles of MgCl2 is equal to twice the number of moles of Cl ions.
Number of moles of MgCl2 = 2 * 0.25 moles/L
Step 4: Calculate the mass of MgCl2.
Mass of MgCl2 = Number of moles * Molar mass
Mass of MgCl2 = (2 * 0.25 moles/L) * 95.21 g/mol
Considering we're making 100mL of the solution, we need to convert the grams of MgCl2 to the appropriate quantity for 100mL.
Step 5: Calculate the mass of MgCl2 required for 100mL.
Mass of MgCl2 required for 100mL = (Mass of MgCl2 / (1000 mL/L)) * 100 mL
Mass of MgCl2 required for 100mL = ((2 * 0.25 moles/L) * 95.21 g/mol) * (100 mL / 1000 mL)
By performing the calculations in Step 5, you will be able to determine the exact mass of MgCl2 needed to dissolve in order to prepare a 100mL solution that is 0.25M in chloride ions.
Molarity= molessolute/liters
molessolute= molarity*liters
gramssolute/MW=molarity*liters
gramssolute= MolWeight*Molarity*liters