A hospital saline solution is analyzed to confirm its concentration. A 60.0 mL sample with a mass of 50.443 g is evaporated to dryness.
(a) If the solid sodium chloride residue has a mass of 0.413 g, find the mass/mass percent concentration of the NaCl solution.
%
(b) Find the molar concentration.
M
Hmmmm. saline should have a density greater than 1g/cc, here it is less :(50.433/60)
To find the mass/mass percent concentration of the NaCl solution, you need to calculate the ratio of the mass of NaCl to the mass of the solution, and then multiply by 100 to express it as a percentage.
(a) Here's how you can find the mass/mass percent concentration:
Step 1: Determine the mass of NaCl in the sample.
The mass of NaCl in the sample is calculated by subtracting the mass of the solid sodium chloride residue from the initial mass of the sample:
Mass of NaCl = Mass of sample - Mass of solid residue
Mass of NaCl = 50.443 g - 0.413 g
Mass of NaCl = 50.03 g
Step 2: Calculate the mass/mass percent concentration.
The mass/mass percent concentration is calculated by dividing the mass of NaCl by the mass of the solution and multiplying by 100:
Mass/mass percent concentration of NaCl = (Mass of NaCl / Mass of solution) × 100
Mass/mass percent concentration of NaCl = (50.03 g / 50.443 g) × 100
Mass/mass percent concentration of NaCl ≈ 99.177%
Therefore, the mass/mass percent concentration of the NaCl solution is approximately 99.177%.
To find the molar concentration of the NaCl solution, you need to use the molar mass of NaCl and the volume of the solution.
(b) Here's how you can find the molar concentration:
Step 1: Determine the number of moles of NaCl.
The number of moles of NaCl can be calculated using its molar mass, which is the sum of the atomic masses of sodium (Na) and chlorine (Cl):
Molar mass of NaCl = atomic mass of Na + atomic mass of Cl
Molar mass of NaCl = 22.99 g/mol + 35.45 g/mol
Molar mass of NaCl = 58.44 g/mol
Number of moles of NaCl = Mass of NaCl / Molar mass of NaCl
Number of moles of NaCl = 0.413 g / 58.44 g/mol
Number of moles of NaCl ≈ 0.00708 mol
Step 2: Calculate the molar concentration.
The molar concentration (or molarity) is calculated by dividing the number of moles of solute by the volume of the solution in liters:
Molar concentration of NaCl = Number of moles of NaCl / Volume of solution (in L)
Molar concentration of NaCl = 0.00708 mol / 0.06 L
Molar concentration of NaCl ≈ 0.118 M (mol/L)
Therefore, the molar concentration of the NaCl solution is approximately 0.118 M.