Answer:
a. Molarity of NaCl solution = 5.64 * 10⁻⁷ mol/L
b. molarity of Na⁺ = 5.64 * 10⁻⁷ mol/L
c. molarity of Cl⁻ = 5.64 * 10⁻⁷ mol/L
d. Osmolarity = 1.128 osmol
e. mass percent of NaCl = 3.30 * 10⁻⁶ %
f. parts per million NaCl = 0.033 ppm NaCl
g. parts per billion of NaCl = 33 ppb of NaCl
h. From the values obtained from e, f and g, the most convenient to use and understand is parts per billion as it has less of a fractional part to deal with especially since the solute concentration is very small.
Explanation:
Molarity of a solution = number of moles of solute (moles)/volume of solution (L)
where number of moles of solute = mass of solute (g)/molar mass of solute (g/mol)
a. Molarity of NaCl:
molar mass of NaCl = 58.5 g/mol, mass of NaCl = 33.0/1000) g = 0.033g
number of moles of NaCl = 0.033/58.5 = 0.000564 moles
Molarity of NaCl solution = 0.000564/1000 = 5.64 * 10⁻⁷ mol/L
b. Equation for the dissociation of NaCl in solution: NaCl ----> Na⁺ + Cl⁻
From the above equation I mole of NaCl dissociates to give 1 mole of Na⁺ ions,
Therefore molarity of Na⁺ = 1 * 5.64 * 10⁻⁷ mol/L = 5.64 * 10⁻⁷ mol/L
c. From the above equation I mole of NaCl dissociates to give 1 mole of Cl⁻ ions,
therefore molarity of Cl⁻ = 1 * 5.64 * 10⁻⁷ mol/L = 5.64 * 10⁻⁷ mol/L
d. From the above equation, dissociation of NaCl in water produces 1 mol Na⁺ and 1 mole Cl⁻.
Total number of particles produced = 2
Osmolarity of solution = number of particles * molarity of siolution
Osmolarity = 2 * 5.64 * 10⁻⁷ mol/L = 1.128 osmol
e. mass of percent of NaCl = {mass of NaCl (g)/ mass of solution (g)} * 100
density of water = 1 Kg/L
mass of water = 1 Kg/L * 1000 L = 1000 kg
1Kg = 1000 g
Therefore mass of solution in g = 1000 * 1000 = 1 * 10⁶ g
mass percent of NaCl = (0.033/1 * 10⁶) * 100 = 3.30 * 10⁻⁶ %
f. Parts per million of NaCl:
parts per million = 1 mg of solute/L of solution
One thousandth of a gram is one milligram and 1000 ml is one liter, so that 1 ppm = 1 mg per liter = mg/Liter.
Since the density of water is 1kg/L = 1,000,000 mg/L
1mg/L = 1mg/1,000,000mg or one part in one million.
parts per million NaCl = 33.0/1000 L = 0.033 ppm NaCl
g. Parts per billion = 1 µg/L of solution
1 g = 1000 µg
therefore, 33.0 mg = 33.0 * 1000 µg = 3.30 * 10⁴ µg
parts per billion of NaCl = 3.30 * 10⁴ µg/1000 L = 33 ppb of NaCl
h. From the values obtained from e, f and g, the most convenient to use and understand is parts per billion as it has less of a fractional part to deal with especially since the solute concentration is very small.
