# 0.8 Metathesis: to exchange or not?

 Page 1 / 4

## 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

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)

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

what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
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?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
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?
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers! By         