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ch4aika [34]
3 years ago
7

If you have an aqueous solution that is 13.5 % Na3PO4 by mass, what is the molality of Na3PO4 in the solution?

Chemistry
1 answer:
Nata [24]3 years ago
7 0

Considering the definition of percentage by mass and molality, the molality of Na₃PO₄ in the solution is 0.948 \frac{moles}{kg}.

  • <u><em>Percentage by mass</em></u>

The percentage by mass expresses the concentration and indicates the amount of mass of solute present in 100 grams of solution.

In other words, the percentage by mass of a component of the solution is defined as the ratio of the mass of the solute to the mass of the solution, expressed as a percentage.

The percentage by mass is calculated as the mass of the solute divided by the mass of the solution, the result of which is multiplied by 100 to give a percentage. This is:

percentage by mass=\frac{mass of solute}{mass of solution}x100

  • <u><em>Molality</em></u>

Molality is the ratio of the number of moles of any dissolved solute to kilograms of solvent.

The Molality of a solution is determined by the expression:

molality=\frac{number of moles of solute}{kilograms of solvent}

  • <u><em>This case</em></u>

Considering 100 grams as a sample of the solution, then the value of the percentage of concentration given indicates that  13.5 g correspond to Na₃PO₄.

Remember that percent concentration by mass is calculated using the mass of solute and the mass of the solution, which includes both the solute and the solvent. Then:

mass solution= mass solute + mass solvent

100 g= 13.5 g + mass solvent

100 g - 13.5 g= mass solvent

<u><em>86.5 g= mass solvent</em></u>

Then, you know:

  • number of moles of solvent=  13.5 gramsx\frac{1 mole}{163.94 grams} =0.082 moles being 163.94 \frac{grams}{mole}the molar mass of Na₃PO₄, this is the amount of mass a substance contains in one mole.
  • mass of solvent= 86.5 grams= 0.0865 kg (being 1000 g= 1 kg)

Then, replacing in the definition of molality:

molality=\frac{0.082 moles}{0.0865 kg}

Solving:

molality= 0.948 \frac{moles}{kg}

Finally, the molality of Na₃PO₄ in the solution is 0.948 \frac{moles}{kg}.

Learn more about:

  • mass percentage:
  1. brainly.com/question/19168984?referrer=searchResults
  2. brainly.com/question/18646836?referrer=searchResults
  3. brainly.com/question/20037730?referrer=searchResults
  4. brainly.com/question/25148948
  • molality
  1. brainly.com/question/20366625?referrer=searchResults
  2. brainly.com/question/4580605?referrer=searchResults

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