Practical Chemistry: Analysis of Water Vapor Pressure Experiment

This practical chemistry assignment focuses on the measurement and analysis of the vapor pressure of water. The experiment explores the relationship between temperature and vapor pressure, examining how changes in temperature affect the kinetic energy of water molecules and their ability to escape into the vapor phase. The assignment includes background theory, discussing concepts such as the combined gas law, Dalton's law, and the Clausius-Clapeyron equation. The student presents experimental setup details, data analysis, and results, including a linear plot of ln(P) versus 1/T. The analysis involves calculating thermodynamic properties like enthalpy and entropy of vaporization and comparing experimental values to theoretical values, with discussions on potential sources of error. The conclusion highlights the dependence of vapor pressure on temperature, the impact on evaporation and condensation rates, and the conditions for equilibrium. References to supporting literature are also included.

Measurement of the Vapor Pressure of Water
Name institution
Background
Kinetic energy of a liquid is usually a function of the temperature of
the liquid; at low temperatures, the molecules have kinetic energy
(Fox, 2010). For molecules to escape to the vapor phase they require
temperature. For equilibrium liquid (Khélifa, 2008).
During the gas phase there are constant random collations of molecules with each other .at the liquid phase, the vapor pressure will
increase. If condensation occurs faster than vaporization at a given temperature, the vapor pressure and the rate of collisions will drop.
These happens repeatedly until a constant phase is achieved.
SETUP
Theory
At the higher temperatures, this is not the case but we can calculate how the partial pressure of the air
changes as the water heats up using the combined gas law.
Dalton’s law tells us that the total pressure is equal to the sum of the partial pressures of the
component gases it follow that at all temperatures:
This gives us pwater, which can be used in conjunction with the Clausius-Chaperon Equation to calculate
_Hvap, _Svap and the normal boiling point of water
Results
0.0028 0.003 0.0032
0
1
2
3
f(x) = 4898.7378272 x − 12.671347337
R² = 0.903643489499438
Linear plot of ln(P) versus 1/T
1/T(T)
ln(P)l
Change in entropy is =131.3
J/K−mol the experimental
value is higher than the
theoretical value of
109J/K−mol. This can be
attributed to errors in data
collection. The calculated
value is within the
range .From the graph water
boils at 98C0 this is lower
than the 100C0 temperature
due to atmospheric pressure
difference,
References
Fox, J. (2010). Measurement of the vapor pressure curve of water. Physics
Education, 28(3), 190-192. doi: 10.1088/0031-9120/28/3/012
Khélifa, N. (2008). Water Vapour Effects in Mass Measurement. Measurement Science
Review, 8(1). doi: 10.2478/v10048-008-0006-y
Conclusion
Vapor pressure for water is a function of the kinetic energy in water. The kinetic
energy is also a function of temperatures of water. If the temperature drops,
evaporation will slow, and condensation will cause a
Decrease in vapor pressure, which will cause a subsequent decrease in the rate of
condensation. When equilibrium is reestablished, the vapor pressure will be a
function of temperature
1/T/K-1 ln pwater
0.002833 -1.23497
0.002879 -1.3171
0.002915 -1.48222
0.002959 -2.01712
0.003003 -2.25584
0.003049 -2.13355
0.003096 -2.43019
From the graph ∆H = to the gradient =4898.7
∆S=48987/373=131.3 J/K−mol