Experiment on Solubility of Gases in Water

May 27, 2024

Experiment on Solubility of Gases in Water

Introduction

  • Objective: To determine how much oxygen and carbon dioxide dissolve in a cup of water.
  • Atmosphere Composition: Oxygen is about 21% of the atmosphere.

Experimental Setup

  • Materials: A cup of water at room temperature (25°C).
  • Initial Measurement: Measure the concentration of oxygen at the top layer of the water.

Measuring Oxygen

  • Initial Steps:
    • Pure water cup placed at room temperature.
    • Calculate concentration of oxygen over time.
  • Oxygen Concentration:
    • Calculated concentration: Approx. 0.27 mmol/L.
    • Use Henry’s Law:
      • Partial Pressure (P) and Concentration (C) can find a constant (KH).
      • KH for oxygen: 769 L·atm/mol.
      • Calculated through division of known figures.

Measuring Carbon Dioxide

  • Atmosphere Simulation: Change to 21% carbon dioxide (hypothetical high concentration).
  • Experimental Steps:
    • Same procedure as oxygen, with CO2 instead.
    • CO2 Concentration:
      • Calculated higher concentration: Approx. 7.24 mmol/L.
      • Diagrams and concentration comparison.
  • Partial Pressure:
    • Similar partial pressures for O2 and CO2 (since atmospheric pressure remains same).
    • Concentration higher for CO2 due to different KH values.

Comparing Solubility

  • KH Values:
    • CO2: 29 L·atm/mol.
    • O2: 769 L·atm/mol.
    • CO2’s KH value is much smaller, indicating much higher solubility.

Detailed Analysis

  • Molecular Interaction:
    • CO2 forms H2CO3 (carbonic acid) with H2O, increasing solubility.
    • O2 does not interact similarly, remains largely undissolved.
  • Formula Reaction: CO2 + H2O -> H2CO3.
    • CO2 more stable in water due to chemical bonding.
    • Product of reaction: Bicarbonate and proton.

Calculation of Relative Solubility

  • Ratio Analysis:
    • CO2 is 26 times more soluble than O2 in water at 25°C.
    • Actual formula comparison: 729 ÷ 29 = 26.
  • Human Body Relevance:
    • Body temperature (37°C) affects solubility.
    • Solubility difference in blood compared to water.

Conclusions

  • Key Findings:
    • CO2 has much higher solubility in water than O2 due to molecular and chemical interactions.
    • Henry’s Law constants and temperature are critical factors.
  • Implications:
    • Understanding gas solubility in water has implications for respiratory physiology and environmental sciences.