# 11.4 Colligative properties  (Page 4/30)

 Page 4 / 30

The extent to which the vapor pressure of a solvent is lowered and the boiling point is elevated depends on the total number of solute particles present in a given amount of solvent, not on the mass or size or chemical identities of the particles. A 1 m aqueous solution of sucrose (342 g/mol) and a 1 m aqueous solution of ethylene glycol (62 g/mol) will exhibit the same boiling point because each solution has one mole of solute particles (molecules) per kilogram of solvent.

## Calculating the boiling point of a solution

What is the boiling point of a 0.33 m solution of a nonvolatile solute in benzene?

## Solution

Use the equation relating boiling point elevation to solute molality to solve this problem in two steps.

1. Calculate the change in boiling point.
$\text{Δ}{T}_{\text{b}}={K}_{\text{b}}m=2.53\phantom{\rule{0.2em}{0ex}}\text{°}\text{C}\phantom{\rule{0.2em}{0ex}}{m}^{-1}\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}0.33\phantom{\rule{0.2em}{0ex}}m=0.83\phantom{\rule{0.2em}{0ex}}\text{°}\text{C}$
2. Add the boiling point elevation to the pure solvent’s boiling point.
$\text{Boiling temperature}=80.1\phantom{\rule{0.2em}{0ex}}\text{°}\text{C}+0.83\phantom{\rule{0.2em}{0ex}}\text{°}\text{C}=80.9\phantom{\rule{0.2em}{0ex}}\text{°}\text{C}$

## Check your learning

What is the boiling point of the antifreeze described in [link] ?

109.2 °C

## The boiling point of an iodine solution

Find the boiling point of a solution of 92.1 g of iodine, I 2 , in 800.0 g of chloroform, CHCl 3 , assuming that the iodine is nonvolatile and that the solution is ideal.

## Solution

We can solve this problem using four steps.

1. Convert from grams to moles of I 2 using the molar mass of I 2 in the unit conversion factor.
Result: 0.363 mol
2. Determine the molality of the solution from the number of moles of solute and the mass of solvent, in kilograms.
Result: 0.454 m
3. Use the direct proportionality between the change in boiling point and molal concentration to determine how much the boiling point changes.
Result: 1.65 °C
4. Determine the new boiling point from the boiling point of the pure solvent and the change.
Result: 62.91 °C
Check each result as a self-assessment.

## Check your learning

What is the boiling point of a solution of 1.0 g of glycerin, C 3 H 5 (OH) 3 , in 47.8 g of water? Assume an ideal solution.

100.12 °C

## Distillation of solutions

Distillation is a technique for separating the components of mixtures that is widely applied in both in the laboratory and in industrial settings. It is used to refine petroleum, to isolate fermentation products, and to purify water. This separation technique involves the controlled heating of a sample mixture to selectively vaporize, condense, and collect one or more components of interest. A typical apparatus for laboratory-scale distillations is shown in [link] .

Oil refineries use large-scale fractional distillation to separate the components of crude oil. The crude oil is heated to high temperatures at the base of a tall fractionating column , vaporizing many of the components that rise within the column. As vaporized components reach adequately cool zones during their ascent, they condense and are collected. The collected liquids are simpler mixtures of hydrocarbons and other petroleum compounds that are of appropriate composition for various applications (e.g., diesel fuel, kerosene, gasoline), as depicted in [link] .

#### Questions & Answers

what is a solution
A liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).
Gabby
what is an acid and base
Joy
acids are substances that ionize (break off) in an aqueous solution to produce hydrogen (H+) ions. pH level less than 7  bases produce hydroxide (OH-) ions in solution. pH level greater than 7
Gabby
An acid is a substances when dissolve in water to produce hydrogen ion as the only positive ion or proton. while base is a substances when dissolve in water to produce hydroxide ion .
Lawal
acid is a substance that produce hydrogen ion as only positive ion when dissolve in water
Ayomide
what is flame
my new mix tape
Jake
What is Stoichiometry?
sir I don't know
favour
the relationship between the relative quantities of substances taking part in a reaction or forming a compound, typically a ratio of whole integers.
Gabby
A radioactive subtance has a half life of 20hrs what fraction of the original radioactive nuclear will remain in 80hrs
1/16th
Ian
general properties of transition metal
form stable complexes Have high melting and boiling points Contain large charge/radius ratio Form compounds which are often paramagnetic Are hard and possess high densities Form compounds with profound catalytic activity Show variable oxidation states form coloured ions and compounds.
Gabby
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am just tried of it😭🙏
Same here
Brianna
organic chem tutor, hell teach you everything.. take notes clearly in a notebook and read it before you go to sleep until you know every topic like the back of your hand
Professor
I find it very hard to understand and remember things I read please I need help. Is just as if chemistry is difficult to me
Precious
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get good or find something else. don't do it if you don't love it
Professor
what is dative bond?
A coordinate covalent bond, also known as a dative bond or coordinate bond is a kind of 2-center, 2-electron covalent bond in which the two electrons derive from the same atom.
dharshika
how can i write iupac nunber
Emmanuel
In chemical nomenclature, the IUPAC nomenclature of organic chemistry is a method of organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry. It is published in the Nomenclature of Organic Chemistry
Nike
How can I know the logic for writing the configuration of an element?
Brianna
s and p diagram
Papa
I dont understand that
Brianna
what is elemental composition of earth
what if we try copper and the hydrogen what happened
law of definite proportion
Law of Definite Proportion states that all pure samples of the same chemical compound contains the same elements in proportion by mass
Eunice
what is chemistry
It is that branch of Science which deals with the study of composition, structure and properties of matter .... Ok
ShAmy
The branch of natural science that deals with the constitution of substances and the changes that they undergo as a consequence of alterations in the constitution of their molecules
Young
what is the constitution of substance
ShAmy
picture of periodic table
what is matter
What are the classes of colloid
percentage composition