What is the molarity of a solution made by dissolving 10 grams of CaBr2 in enough water to make 400 mL of solution?
moles = grams/molar mass
M = moles/L
To find the molarity of a solution, we need to know the amount of solute (in moles) and the volume of the solution (in liters). In this case, we're given the mass of the solute (10 grams of CaBr2) and the volume of the solution (400 mL).
1. Convert the volume of the solution from milliliters (mL) to liters (L).
To do this, divide the volume by 1000: 400 mL ÷ 1000 = 0.4 L.
2. Calculate the amount of solute in moles.
To find the number of moles, we need to know the molar mass of CaBr2. The molar mass for calcium bromide (CaBr2) is calculated as follows:
Ca (40.08 g/mol) + 2Br (2 × 79.90 g/mol) = 40.08 g/mol + 159.80 g/mol = 199.88 g/mol.
Divide the mass of the solute by its molar mass to find the number of moles: 10 g ÷ 199.88 g/mol ≈ 0.05 mol.
3. Calculate the molarity of the solution.
The molarity (M) is defined as the number of moles of solute divided by the volume of the solution in liters.
Molarity = moles of solute / volume of solution (in L).
Molarity = 0.05 mol / 0.4 L ≈ 0.125 M.
Therefore, the molarity of the solution made by dissolving 10 grams of CaBr2 in enough water to make 400 mL of solution is approximately 0.125 M.