How many millimoles of solute are contained in

/ Exams & Certification / By

How many millimoles of solute are contained in

(a) 2.00 L of 2.76 X 10-3 M KMnO4?

(b) 250.0 mL of 0.0423 M KSCN?

(c) 500.0 mL of a solution containing 2.97 ppm CuSO4?

(d) 2.50 L of 0.352 M KCl?

The correct answer and explanation is :

To calculate the number of millimoles (mmol) of solute, we use the following formula:

[
\text{Millimoles of solute} = \text{Concentration (in mol/L)} \times \text{Volume (in L)} \times 1000
]

The factor of 1000 is used to convert moles to millimoles (since 1 mol = 1000 mmol).

(a) 2.00 L of 2.76 × 10⁻³ M KMnO₄

Given:

  • Concentration (M) = 2.76 × 10⁻³ M
  • Volume (L) = 2.00 L

First, we apply the formula:
[
\text{Millimoles of KMnO₄} = 2.76 \times 10^{-3} \, \text{M} \times 2.00 \, \text{L} \times 1000 = 5.52 \, \text{mmol}
]

So, the number of millimoles of KMnO₄ in 2.00 L of solution is 5.52 mmol.

(b) 250.0 mL of 0.0423 M KSCN

Given:

  • Concentration (M) = 0.0423 M
  • Volume (mL) = 250.0 mL = 0.2500 L (since 1000 mL = 1 L)

Using the formula:
[
\text{Millimoles of KSCN} = 0.0423 \, \text{M} \times 0.2500 \, \text{L} \times 1000 = 10.575 \, \text{mmol}
]

So, the number of millimoles of KSCN in 250.0 mL of solution is 10.575 mmol.

(c) 500.0 mL of a solution containing 2.97 ppm CuSO₄

Given:

  • Concentration in ppm (parts per million) = 2.97 ppm
  • Volume (mL) = 500.0 mL = 0.5000 L
  • 1 ppm is equivalent to 1 mg/L, so the concentration is 2.97 mg/L.

To convert the concentration from milligrams to moles, we need to use the molar mass of CuSO₄. The molar mass of CuSO₄ is:
[
\text{Molar mass of CuSO₄} = 63.55 (\text{Cu}) + 32.07 (\text{S}) + 4 \times 16.00 (\text{O}) = 159.62 \, \text{g/mol}
]

Now, convert the concentration to moles per liter:
[
\text{Concentration (mol/L)} = \frac{2.97 \, \text{mg/L}}{159.62 \, \text{g/mol}} = \frac{2.97 \times 10^{-3} \, \text{g/L}}{159.62 \, \text{g/mol}} = 1.86 \times 10^{-5} \, \text{mol/L}
]

Now, calculate the millimoles:
[
\text{Millimoles of CuSO₄} = 1.86 \times 10^{-5} \, \text{mol/L} \times 0.5000 \, \text{L} \times 1000 = 0.0093 \, \text{mmol}
]

So, the number of millimoles of CuSO₄ in 500.0 mL of solution is 0.0093 mmol.

(d) 2.50 L of 0.352 M KCl

Given:

  • Concentration (M) = 0.352 M
  • Volume (L) = 2.50 L

Using the formula:
[
\text{Millimoles of KCl} = 0.352 \, \text{M} \times 2.50 \, \text{L} \times 1000 = 880 \, \text{mmol}
]

So, the number of millimoles of KCl in 2.50 L of solution is 880 mmol.

Summary of Answers:

  • (a) 5.52 mmol of KMnO₄
  • (b) 10.575 mmol of KSCN
  • (c) 0.0093 mmol of CuSO₄
  • (d) 880 mmol of KCl

These calculations demonstrate how to convert molarity and volume into the number of millimoles of solute present in a solution.

Related Posts

Scroll to Top