EXPERIMENT NO. 6
GAS LAWS
OBJECTIVES
To demonstrate the combined gas law
To compute the molar mass of ammonia by using Grahams law of diffusion
CONCLUSION
Conclusion of this experiment no. 6 about gas laws can be stated that the combined gas law combines Charles’s law, Boyle’s law, and Gay-Lussac’s law. These laws each relate one thermodynamic variable to another mathematically while holding everything else constant. Charles’s law states that volume and temperature are directly proportional to each other as long as pressure is held constant. Boyle's law asserts that pressure and volume are inversely proportional to each other at fixed temperature. Finally, Gay-Lussac's law introduces a direct proportionality between temperature and pressure as long as it is at a constant volume.
Grahams law of diffusion states that the rates of diffusion for gases are inversely proportional to the square roots of their molar masses under the same conditions of temperature and pressure. The rate of diffusion is equal to the distance traveled divided by the time of travel of the gas. Since temperatures are equal to each other, we can wire the equation as:
M d
=
M d
We can substitute the chemical equation HCl + NH ® NH Cl and simplify the equation as and compute for the experimental Molar Mass of Ammonia.
MHCl(dHCl)² 36.46g/mol (12.3cm)²
MNH = = = 17.60 g/mol
(dNH )² (17.7cm)²
The computed experimental Molar Mass of the ammonia is 17.60 g/mol and the given molar mass of hydrogen chloride is 36.46 g/mol. The ammonia traveled on the glass tubing longer distance because the mass of the hydrogen chloride is heavier compared to the mass of ammonia.