# 0.8 Metathesis: to exchange or not?

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## Objectives

• To give practice writing equations for metathesis reactions, including net ionic equations
• To illustrate the concept of solubility and the effect of temperature and crystallization

## Grading

You will be determined according to the following:

• Pre-lab (10%)
• Must attach graph
• Lab Report Form (80%)
• Must include detailed observations for each reaction
• TA Evaluation of lab procedure (10%)

## Before coming to lab…

• Complete the pre-lab exercise, including the plot (due at the beginning of lab)
• Read the instructions for the lab and refresh your memory on anything that isn’t clear by reading your textbook

## Introduction

In molecular equations for many aqueous reactions, cations and anions appear to exchange partners. These reactions conform to the following general equation:

Equation 1: $\text{AX}+\text{BY}\to \text{AY}+\text{BX}$

These reactions are known as metathesis reactions. For a metathesis reaction to lead to a net change in solution, ions must be removed from the solution. In general, three chemical processes can lead to the removal of ions from solution, comcomitantly serving as a driving force for metathesis to occur:

1. The formation of a precipitate2. The formation of a weak electrolyte or nonelectrolyte3. The formation of a gas that escapes from solution

The reaction of barium chloride with silver nitrate is a typical example:

Equation 2: ${\text{BaCl}}_{2}\left(\text{aq}\right)+{\text{2AgNO}}_{3}\left(\text{aq}\right)\to \text{Ba}\left({\text{NO}}_{3}{\right)}_{2}\left(\text{aq}\right)+\text{2AgCl}\left(s\right)$

This form of the equation for this reaction is referred to as the molecular equations. Since we know that the salts ${\text{BaCl}}_{2}$ , ${\text{AgNO}}_{3}$ , and $\text{Ba}\left({\text{NO}}_{3}{\right)}_{2}$ are strong electrolytes and are completely dissociated in solution, we can more realistically write the equation as follows:

Equation 3: ${\text{Ba}}^{2+}\left(\text{aq}\right)+{\text{2Cl}}^{-}\left(\text{aq}\right)+{\text{2Ag}}^{+}\left(\text{aq}\right)+{\text{2NO}}_{{3}^{-}}\left(\text{aq}\right)\to {\text{Ba}}^{2+}\left(\text{aq}\right)+{\text{2NO}}_{{3}^{-}}\left(\text{aq}\right)+\text{2AgCl}\left(s\right)$

This form, in which all ions are shown, is known as the complete ionic equation. Reaction occurs because the insoluble substance AgCl precipitates out of solution. The other product, barium nitrate, is soluble in water and remains in solution. We see that ${\text{Ba}}^{2+}$ and ${\text{NO}}_{{3}^{-}}$ ions appear on both sides of the equation and thus do not enter into the reaction. Such ions are called spectator ions. If we eliminate or omit them from both sides, we obtain the net ionic equation:

Equation 4: ${\text{Ag}}^{+}\left(\text{aq}\right)+{\text{Cl}}^{-}\left(\text{aq}\right)\to \text{AgCl}\left(s\right)$

This equation focuses our attention on the salient feature of the reaction: the formation of the precipitate AgCl. It tells us that solutions of any soluble ${\text{Ag}}^{+}\text{salt}$ and any soluble ${\text{Cl}}^{-}\text{salt}$ , when mixed, will form insoluble AgCl. When writing net ionic equations, remember that only strong electrolytes are written in the ionic form. Solids, gases, nonelectrolytes, and weak electrolytes are written in the molecular form. Frequently the symbol (aq) is omitted from ionic equations. The symbols (g) for gas and (s) for solid should not be omitted. Thus, Equation 4 can be written as

Equation 5: ${\text{Ag}}^{+}+{\text{Cl}}^{-}\to \text{AgCl}\left(s\right)$

Consider mixing solutions of KCl and ${\text{NaNO}}_{3}$ . The ionic equation for the reaction is

Equation 6: ${K}^{+}\left(\text{aq}\right)+{\text{Cl}}^{-}\left(\text{aq}\right)+{\text{Na}}^{+}\left(\text{aq}\right)+{\text{NO}}_{{3}^{-}}\left(\text{aq}\right)\to {K}^{+}\left(\text{aq}\right)+{\text{NO}}_{{3}^{-}}\left(\text{aq}\right)+{\text{Na}}^{+}\left(\text{aq}\right)+{\text{Cl}}^{-}\left(\text{aq}\right)$

#### Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Gen chem lab. OpenStax CNX. Oct 12, 2009 Download for free at http://cnx.org/content/col10452/1.51
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