Find the amount in millimoles of the indicated species in

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Find the amount in millimoles of the indicated species in

(a) 850 mg of P2O5.

(b) 40.0 g of CO2.

(c) 12.92 g of NaHCO3.

(d) 57 mg of MgNH4PO4.

  1. Find the number of millimoles of solute in

(a) 2.00 L of 0.0555 M KMnO4.

(b) 750 mL of 3.25 X 10-3 M KSCN.

(c) 3.50 L of a solution that contains 3.33 ppm of CuSO4.

(d) 250 mL of 0.414 M KCl.

The Correct Answer and Explanation is :

To determine the amount in millimoles (mmol) of a given species, we can use the following general approaches:

  1. For solid compounds: Convert the mass of the compound to moles by dividing by its molar mass, then multiply by 1,000 to convert to millimoles.
  2. For solutions: Multiply the volume of the solution (in liters) by its molarity (in moles per liter), then multiply by 1,000 to convert to millimoles.

Let’s apply these methods to each part of your question:

(a) 850 mg of P₂O₅

  • Convert mass to grams: 50 mg = 0.850 g- Calculate molar mass of P₂O₅:
    • Phosphorus (P): 0.97 g/mol – Oxygen (O): 6.00 g/mol – Molar mass of P₂O₅ = 2 × 30.97) + (5 × 16.00) = 141.94 g/mol- Calculate moles: .850 g ÷ 141.94 g/mol ≈ 0.00599 mol- Convert to millimoles: .00599 mol × 1,000 ≈ 5.99 mmol (b) 40.0 g of CO₂
  • Calculate molar mass of CO₂:
    • Carbon (C): 2.01 g/mol – Oxygen (O): 6.00 g/mol – Molar mass of CO₂ = 2.01 + (2 × 16.00) = 44.01 g/mol- Calculate moles: 0.0 g ÷ 44.01 g/mol ≈ 0.909 mol- Convert to millimoles: .909 mol × 1,000 ≈ 909 mmol (c) 12.92 g of NaHCO₃
  • Calculate molar mass of NaHCO₃:
    • Sodium (Na): 2.99 g/mol – Hydrogen (H): .01 g/mol – Carbon (C): 2.01 g/mol – Oxygen (O): 6.00 g/mol – Molar mass of NaHCO₃ = 2.99 + 1.01 + 12.01 + (3 × 16.00) = 84.01 g/mol- Calculate moles: 2.92 g ÷ 84.01 g/mol ≈ 0.1538 mol- Convert to millimoles: .1538 mol × 1,000 ≈ 153.8 mmol (d) 57 mg of MgNH₄PO₄
  • Convert mass to grams: 7 mg = 0.057 g- Calculate molar mass of MgNH₄PO₄:
    • Magnesium (Mg): 4.31 g/mol – Nitrogen (N): 4.01 g/mol – Hydrogen (H): .01 g/mol – Phosphorus (P): 0.97 g/mol – Oxygen (O): 6.00 g/mol – Molar mass of MgNH₄PO₄ = 4.31 + 14.01 + (4 × 1.01) + 30.97 + (4 × 16.00) = 137.33 g/mol- Calculate moles: .057 g ÷ 137.33 g/mol ≈ 0.000415 mol- Convert to millimoles: .000415 mol × 1,000 ≈ 0.415 mmol 1. (a) 2.00 L of 0.0555 M KMnO₄
  • Calculate moles: .00 L × 0.0555 mol/L = 0.111 mol- Convert to millimoles: .111 mol × 1,000 = 111 mmol (b) 750 mL of 3.25 × 10⁻³ M KSCN
  • Convert volume to liters: 50 mL = 0.750 L- Calculate moles: .750 L × 3.25 × 10⁻³ mol/L = 0.0024375 mol- Convert to millimoles: .0024375 mol × 1,000 ≈ 2.44 mmol (c) 3.50 L of a solution that contains 3.33 ppm of CuSO₄
  • Understand ppm: .33 ppm means 3.33 mg of CuSO₄ per liter of solution.- Total mass of CuSO₄: .33 mg/L × 3.50 L = 11.655 mg- Convert mass to grams: 1.655 mg = 0.011655 g- Calculate molar mass of CuSO₄:
    • Copper (Cu): 3.55 g/mol – Sulfur (S): 2.07 g/mol – Oxygen (O): 6.00 g/mol – Molar mass of CuSO₄ = 3.55 + 32.07 + (4 × 16.00) = 159.61 g/mol- Calculate moles: .011655 g ÷ 159

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