Calculating Molality of a Sulfuric Acid Solution

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SUMMARY

The discussion focuses on calculating the molality of a 77.0% sulfuric acid (H2SO4) solution with a density of 1.303 g/mL. To find molality, one must first express the percentage concentration as a fraction, understanding that 77.0% indicates 77 grams of solute in a 100-gram solution. The solvent is determined by subtracting the mass of the solute from the total mass of the solution, resulting in 23 grams of solvent. Finally, the number of moles of H2SO4 is calculated using its molecular weight, which is essential for determining the molality in moles of solute per kilogram of solvent.

PREREQUISITES
  • Understanding of molality and its definition as moles of solute per kilogram of solvent.
  • Knowledge of the molecular weight of sulfuric acid (H2SO4).
  • Ability to perform unit conversions, particularly from grams to kilograms.
  • Familiarity with density and its role in solution calculations.
NEXT STEPS
  • Calculate the molality of sulfuric acid solutions with varying concentrations.
  • Learn about the molecular weight of common acids and their implications in solution chemistry.
  • Explore the relationship between density and molarity in solution calculations.
  • Investigate the properties and uses of sulfuric acid in industrial applications.
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Chemistry students, educators, and professionals involved in solution preparation and analysis, particularly those working with acid-base chemistry and solution concentration calculations.

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Homework Statement


You are given a 77.0% solution of sulfuric acid, H2SO4. What is the molality of this solution? The density of the H2SO4 solution is 1.303 g/mL.


Homework Equations





The Attempt at a Solution


I know I divide 77.0 by 100, and then I have no idea from there.
 
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Molality means the number of moles of solute in one kilogram of SOLVENT.

Express your percentage concentration as a fraction or ratio, using a numerator and a denominator. You are given the density of solution, and you may need the the molecular weight of H2SO4. Your targe result is to be in moles of H2SO4 per kilogram of water. You should obviously understand that 77.0% means \frac{77}{100}.
 
Molality means moles solute over kg solvent but it did not say the solution was aqueous, so do not assume the solvent is water. Assume 77g in 100g solution. 100g-77g=23g solvent. Convert to kg solvent. Last step would be to convert the 77g sulfuric acid to moles using the molecular weight from the periodic table. If you need to convert to Molarity also, that's where the density conversion factor will be needed.
 

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