Heat of Mixing

Heat of Mixing - 1 Marc Pomi 106040098 Professor Johnson...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Marc Pomi 106040098 Professor Johnson and Professor Oatis 10/21/09 Heat of Mixing: Ethanol and Water Abstract The temperature change when known amounts of water and ethanol were mixed was determined to see the enthalpy change in an isothermal and isobaric environment. Agreeable data was found compared to similar experiments. As the mole fraction increased of the solution so did the enthalpy until a certain limit of about 0.32. Since water’s structure and unique properties affect many aspects of a solution, the solutions enthalpy’s decreased at a certain time due to ethanol’s non-electrolyte nature. I. Introduction Water is the most essential molecule to life. Many processes by organisms and the environment are affected from the properties of water. A basic chemical operation is the solving of a compound into water. Water’s unique polarity creates partial charges which fuel these simple reactions. Johnson and Oatis (1) state that entropy is one of many reasons why a substance dissolves into another. Since nature tends to go towards a more random state, entropy is a significant factor. Other forces such as neutralization and changes in volume also play a role. As long as change in Gibbs free energy is negative a solution will be formed.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 According to Johnson and Oatis (1), depending on the interactions of the solute and solvents, the change in the enthalpy of solution can be either positive or negative. The reaction can be endothermic and driven by entropy even if the interactions of solute are greater than the solvent. In water based solutions an important role of the molecule are the hydrogen bonds that form. Since alcohols are hydrophilic (miscible with water) at one end and hydrophobic (immiscible with water) on the other, they may or may not dissolve. An interest in the change of temperature of alcohol when dissolved in water is examined to determine the bonding interactions between ethanol and water. The interactions can either produce heat or absorb heat depending on many factors including a few mentioned before. II. Theory For an isothermal and an isobaric process, the ΔH 0 sol was determined over several compositions of ethanol and water. By mixing known quantities of ethanol and water and measuring the temperature change the ΔH 0 sol was determined. Assuming Cp is the heat capacity of the solution plus the apparatus, and Q is a quantity of heat that produces the temperature change Δ T the heat of mixing was determined as follows: Equation 1: Q mix = -ΔH 0 sol = ⌠ T2 T T1 C p dt = C p ΔT mix Since an adiabatic system cannot be attained, heat calibrations are utilized by using known amounts of electrical energy into the solution and observing temperature rise. The electrical energy was found as follows assuming V is voltage and R is resistance: Equation 2: Q el = (V 2 /R)t = ⌠ T2 T T1 C p dt = C p ΔT el Q mix can then be put into a ratio form with equations 1 and 2 to produce: Equation 3: Q mix = ( ΔT mix \ ΔT el ) Q el
Background image of page 2
3 Another challenge arose since temperature change is affected by many factors which can leak
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/09/2009 for the course CHE 303 taught by Professor Staff during the Fall '08 term at SUNY Stony Brook.

Page1 / 11

Heat of Mixing - 1 Marc Pomi 106040098 Professor Johnson...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online