Molality Calculation: How Much NaCl is Needed for a 0.35 Molal Solution?

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SUMMARY

The discussion focuses on calculating the mass of sodium chloride (NaCl) required to create a 0.35 molal solution in 750 grams of water. The correct answer is determined to be 7.59 grams of NaCl. The calculation involves using the formula for molality, which is defined as the number of moles of solute per kilogram of solvent. The molecular weight of NaCl is established as 58.45 g/mole, which is essential for converting moles to grams.

PREREQUISITES
  • Understanding of molality and its formula
  • Knowledge of molecular weight calculations
  • Basic algebra for solving equations
  • Familiarity with unit conversions (grams to kilograms)
NEXT STEPS
  • Study the concept of molality in detail
  • Learn how to calculate molecular weights of various compounds
  • Explore the implications of solute concentration on solution properties
  • Practice solving similar problems involving different solutes and concentrations
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Chemistry students, educators, and anyone involved in laboratory work requiring solution preparation and concentration calculations.

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Homework Statement


How many grams of NaCl must you add to 750g of water to make a 0.35 molal solution?

Ans. 7.59g

Homework Equations


molality=\frac{mol_{solute}}{kg_{solvent}}
MW of NaCl = 23 + 35.45 = 58.45 g/mole

The Attempt at a Solution


0.35mol/kg=\frac{mass(\frac{1mole}{58.45g})}{0.750kg}
mass = 15.33g
 
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