o make 100mL of a solution that is .25M in chloride ion, how many grams of MgCl2 would you need to dissolve
17 years ago
11 months ago
To determine the number of grams of MgCl2 needed to make a 100mL solution that is 0.25M in chloride ion, you will need to follow these steps:
Step 1: Understand the concept
Molarity (M) is defined as the number of moles of solute per liter of solution. To calculate the number of moles, you can use the formula:
Moles = Molarity ร Volume (in liters)
Step 2: Convert the volume to liters
In this case, the volume given is 100mL. You need to convert it to liters by dividing by 1000:
Volume (in liters) = 100mL รท 1000 = 0.1L
Step 3: Calculate the moles of chloride ion
Since MgCl2 dissociates to form two chloride ions (Cl-), the moles of chloride ions will be twice the molarity:
Moles of chloride ion = 0.25M ร 0.1L ร 2 = 0.05 moles
Step 4: Calculate the molar mass of MgCl2
The molar mass of MgCl2 can be found by summing the atomic masses of magnesium (Mg) and two chlorine atoms (Cl):
Molar mass of MgCl2 = (1 ร atomic mass of Mg) + (2 ร atomic mass of Cl)
Using the atomic masses of Mg (24.31 g/mol) and Cl (35.45 g/mol):
Molar mass of MgCl2 = (24.31) + (2 ร 35.45) = 95.21 g/mol
Step 5: Calculate the mass of MgCl2
You can now calculate the mass of MgCl2 needed using the moles of chloride ion and the molar mass:
Mass of MgCl2 = Moles of chloride ion ร Molar mass of MgCl2
Mass of MgCl2 = 0.05 moles ร 95.21 g/mol โ 4.7605 grams
Therefore, you would need approximately 4.7605 grams of MgCl2 to dissolve in water to make a 0.25M chloride ion solution with a volume of 100 mL.