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Colligative Properties and Ice Cream

Objectives

  • To record facile and fast data collection from the computer interface, ubiquitous in industry and, in this case, to calculate the molecular weight of the unknown solute using freezing point depression
  • To learn the definition of molality and the importance of molality in colligative property calculations
  • To learn to calculate the molality of a solution
  • To measure the freezing point depression caused when adding antifreeze to tert-butanol
  • To calculate the molecular weight of the unknown solute using freezing point depression

Grading

You will be determined according to the following:

  • Pre-lab (10%)
  • Lab Report Form (80%) – including temperature plots
  • TA evaluation of lab procedure (10%)

Introduction

Although colligative properties involve solutions, they do not depend on the interactions between the solvent and the solute molecules but rather on the number of solute particles dissolved in solution. Colligative properties include vapor pressure lowering, osmotic pressure, boiling point elevation, and freezing point depression. In this experiment you will explore freezing point depression using a solution of ethylene glycol in tert-butanol. You will then use freezing point depression to calculate the molar mass of an unknown solute that is dissolved in tert-butanol.

Ethylene glycol, (CH2OH)2 the major component of antifreeze, is a large organic molecule that dissolves easily in water. The structure of ethylene glycol is shown in Figure 1.

Antifreeze keeps the water in a car's radiator from freezing because the ethylene glycol molecules get in the way when water tries to crystallize into ice. It is more difficult for the ice crystals to form, due to the fact that the water must be at a lower kinetic energy. Therefore, the water freezes at a lower temperature than if the glycol molecules were not present. The effect of the ethylene glycol molecules present in a solutioncan be quantified by the following equation:

ΔT = iKfm Equation 1

where Δ T = Tpure - Tsolution, the difference between the freezing temperature of the pure solute and the freezing temperature of the solution. Kf is the freezing point depression constant of the solvent, having units of °C/m, and m is concentration of the solution using units of molality. This equation reflects the fact that a more concentrated solution results in a greater change in freezing temperature.

Most of the previous work that we have done with solutions probably has involved units of molarity, or moles per liter of solution. Freezing point depression calculations (as well as those for boiling point elevation) use molality, or moles of solute per kilogram of solvent. By definition, a freezing point depression or boiling point elevation involves a change in temperature. When the temperature of a solution changes, its volume also changes. Since molarity depends on the volume of the solution, a change in temperature will change the solution's molarity. Molality depends on the mass of the solvent, and this does not change with temperature.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
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Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
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Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, General chemistry lab spring. OpenStax CNX. Apr 03, 2009 Download for free at http://cnx.org/content/col10506/1.56
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