Displacement/
Replacement
Reactions
What is Single Replacement?

When one element replaces another element in a
compound, a single replacement (also known as
displacement) reaction has taken place.
Ex. Cl2 + 2NaBr  2NaCl + Br2
Activity Series
A
single replacement reaction will only take
place if a more reactive metal or halogen is
replacing a less reactive one.
 In
order to know if one element is more reactive
than another, we must look at an activity series
chart

An activity series is a ranking of relative reactivity
of metals and halogens in displacement reactions.
The most reactive elements are at the top of the
activity series, and as you go down the chart the
elements become less reactive.
Single Replacement
Reversibility

Just because a formula is written doesn't
necessarily mean the reaction can take place.
Single Replacement reactions can not be
reversed.

Ex.


Cl2 + 2NaBr --> 2NaCl + Br2
2NaCl + Br2--> Cl2 + 2NaBr
will happen
will not happen
**Chlorine is stronger than bromine**
Activity Series Practice

Determine IF the following reactions will take
place (YES/NO)
1. K + H2O YES
2. Cu + H2SO4 NO
3. FeCl2 + Zn YES
4. Copper (II) sulfate + chromium YES
5. Magnesium + water NO
6. Lead (II) chloride + fluorine YES
Predicting Products of a Single
Displacement Reaction
 If
the reaction takes place, one of three
scenarios take place



1. a halogen (group 17) replaces another
halogen
2. a metal replace another metal
3. a metal replaces hydrogen (in an acid or
water)
 An
acid is just an ionic compound with
hydrogen (Ex. H2SO4)
 When a metal replaces hydrogen in water,
you need to think of water as “hydrogen
hydroxide, H+ OH-”
Predicting Halogen Replacement
Predicting from names:

When a halogen replaces another halogen, the names just
switch places on the right side
Ex. sodium bromide + chlorine  sodium chloride + bromine
 Don’t confuse –ide (in a compound) with –ine (pure element)

Predicting from formulas:


Both sides will not have the same number of atoms until
balanced since pure halogens are diatomic
To not confuse yourself, you can convert formula to name
before figuring out the right side

Ex. NaBr + Cl2  NaCl + Br2 (NOT: NaCl2 + Br)
Practice:
1.
magnesium chloride + fluorine 
2.
KI + F2  (answer is NOT KF2 + I)
(HINT: If it helps, find the answer in words then convert to formula)
Predicting Metal/Metal Replacement
Predicting from names:

Again, the names just switch places and you don’t have to worry
about suffixes

Ex. calcium chlorate + sodium  sodium chlorate + calcium
Predicting from formulas:


Both sides will not necessarily have the same number of atoms
until balanced because metals with different charges will
combine in a different ratio
To not confuse yourself, you can convert formula to name before
figuring out the right side

Ex. Ca(ClO3)2 + Na  NaClO3 + Ca
Practice:
1.
Chromium (III)phosphate + zinc 
2.
Al(SO4)3 + Fe(II) 
(Ca2+ vs. Na+)
(HINT: If it helps, find the answer in words then convert to formula)
Predicting metals replacing hydrogen
Predicting from names:


Again, the names just switch places
If the hydrogen is in water, think of water as hydrogen hydroxide


Ex 1. barium + water  barium hydroxide + hydrogen
Ex 2. aluminum + hydrogen sulfate  aluminum sulfate + hydrogen
Predicting from formulas:


Both sides will not necessarily have the same number of atoms
until balanced because metals with different charges will
combine in a different ratio
To not confuse yourself, you can convert formula to name
before figuring out the right side


Ex 1. Ba + H2O  Ba(OH)2 + H2
Ex 2. Al + H2SO4  Al2(SO4)3 + H2
Practice:
1.
Potassium + water 
2.
Zn + HCl 
(Ba2+ vs. H+)
(Al3+ vs. H+)
Double
Displacement/Replacement
Reactions

Occurs by mixing together two aqueous solutions

2 types:
precipitation reaction
1.

2.
forming a solid from 2 solutions
acid/base neutralization reaction

forming H2O from an acidic and a basic solution
Precipitation Reactions

A solid ionic precipitate (salt) is formed from two ionic aqueous
solutions

When predicting the products in the reaction, the ions switch
places
Ex. silver nitrate + sodium chloride  silver chloride + sodium nitrate
Ex. AgNO3 + NaCl  AgCl + NaNO3

A reaction will only happen if one of the products are insoluble in
water



Solubility is determined by referencing the products on a solubility
chart
The insoluble product will say either A, P or I on the chart
If none of the products say either A, P or I on the chart, there is NO
REACTION,

the new solution created is just a homogenous mixture of the reactants
Practice: Which product is the precipitate in the example reaction above?
Neutralization Reaction

Water is formed from an acid and a base


Acids contain H+
Bases contain OH-
Ex. hydrogen chloride + sodium hydroxide 
sodium chloride + hydrogen hydroxide (water)
Ex. HCl + NaOH  NaCl + HOH (H2O)

Acids and bases always cancel each other
out so there will always be a reaction taking
place