Molecular weights -- Calculate molecular weights of the compounds: Sodium bicarb

Question

Molecular weights -- Calculate molecular weights of the compounds: Sodium bicarbonate (baking soda) -- NaHCO_3 Ferric Chloride -- FeCl_3 Ammonium sulfate -- (NH_4)_2SO_4 Molar and mass concentrations If the molar concentration of sodium bicarbonate (NaHCO_3) is 2.00 mM (mill molar), what is the mass concentration of NaHCO_3 (in mg/L)? For the same molar concentration, what is the mass concentration of Na^+? What are the molar concentrations of iron (Fe^3+) and chloride (Cl^-) in a solution with a mass concentration of 40.7 mg/L FeCl_3?

Explanation / Answer

Answer:

(a) NaHCO3 = 23+1+ 12+ 16x3 = 84 g/mol

           (b) FeCl3 = 55.85 + 35.45 x 3 = 162.2 g/mol

           (c) (NH4)2SO4 = 132.14 g/mol

2. (a) NaHCO3 = 2.0 mM

Molar mass of NaHCO3 is 84 g/mol

84 g of NaHCO3 in 1 litre = 1M

168 g of NaHCO3 in 1 litre= 2 M

168 mg of NaHCO3 in 1 litre = 2 mM

Answer =168 mg/L

(b)

mass concentration = mass / volume

Weight of Na in 2mM = 23mg = 0.023g

=0.023g/L

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