How many grams of calcium nitrate, Ca(NO3)2, are needed to make 100 mL of a .5 M solution?
moles need = M x L.
Solve for moles.
moles = grams/molar mass.
Solve for grams.
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To determine the number of grams of calcium nitrate needed to make a 0.5 M solution, you need to know the molar mass of calcium nitrate (Ca(NO3)2) and the volume of the solution.
Step 1: Find the molar mass of calcium nitrate (Ca(NO3)2).
The molar mass of calcium (Ca) is 40.08 grams/mol.
The molar mass of nitrogen (N) is 14.01 grams/mol.
The molar mass of oxygen (O) is 16.00 grams/mol.
Now, calculate the molar mass of calcium nitrate:
Molar mass of Ca(NO3)2 = (1 * 40.08 g/mol) + (2 * 14.01 g/mol) + (6 * 16.00 g/mol) = 164.09 g/mol.
Step 2: Calculate the mass of calcium nitrate needed for the desired solution.
The molarity (M) is defined as the number of moles of solute per liter of solution. In this case, we have a 0.5 M solution and a volume of 100 mL (0.1 L). Rearrange the formula to solve for moles of solute:
Molarity (M) = Moles of solute / Volume of solution (L)
Rearranging the formula gives:
Moles of solute = Molarity (M) * Volume of solution (L)
Substituting the given values:
Moles of solute = 0.5 mol/L * 0.1 L = 0.05 moles.
Step 3: Calculate the mass of calcium nitrate.
Mass of calcium nitrate = Moles of solute * Molar mass of Ca(NO3)2.
Substituting the values:
Mass of calcium nitrate = 0.05 moles * 164.09 g/mol = 8.20 grams.
Therefore, you would need 8.20 grams of calcium nitrate to make 100 mL of a 0.5 M solution.