What is a chemical reaction?. When reactants are converted to products, bonds holding the atoms together are broken and new bonds are formed. Reactants Products Recall that atoms themselves are neither created nor destroyed; they are merely rearranged.
When reactants are converted to products, bonds holding the atoms together are broken and new bonds are formed.
Recall that atoms themselves are neither created nor destroyed; they are merely rearranged.
Chemical reactions can be described using words.
Either “Iron reacts with oxygen to produce iron (III) oxide (rust)”
Or Iron + Oxygen iron (III) oxide
Easier to use chemical shorthand to represent chemical relationships
Reactants on the left of the arrow and products to the right of the arrow
Fe (s) + O2(g) Fe2O3(s)
Where (s)= solid
(l) = liquid
(g) = gas
(aq)= aqueous solution (dissolved in water)
Heat or catalyst added to a reaction would appear above the arrow. See Table 8.1
H2(g) + O2 (g) H2O(l)
Recall that matter is neither created or destroyed, so what is wrong with this picture?
It’s not balanced, we lost an oxygen, this is not possible so we balance the equation with coefficients, whole numbers that are placed in front representing the relative quantities of each compound.
2 H2(g) + O2 (g) 2 H2O(l)
Now both sides are equal.
Types of chemical equations
POD—for extra credit
Questions on lab? Homework?
Types of Reactions Powerpoint
Two or more substances combine to form a single substance, or…
Two or more products combine to form a single product.
Mg(s) + O2 (g) MgO(s)
Metal + Non-Metal -- Ionic Compound
K + Cl2 KCl
Non-metal + Non-Metal (more than one product possible)
S + O2 SO2 or SO3
Non-metal oxide + H2O acid
SO2 + H2O H2SO4
Metallic oxide + H2O metal hydroxide
CaO + H2O Ca (OH)2
A decomposition reactionis one in which a single compound breaks down into two or more elements or new compounds.
Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.
Hard to predict! usually a gas or element!
CaCO3(s) CaO(s) + CO2(g)
In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light.
Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a combination reaction.
Element + Oxygen oxides
Mg + O2 MgO
Hydrocarbons (or alcohols) + Oxygen CO2 + H2O
CH4 + O2 CO2 + H2O
A + BX → AX + B
Cu + AgNO3 Ag + CuNO3
Predicting Products —
if the activity of the metal is higher than the metal cation in solution there will be a reaction, otherwise there is not a reaction.
What is happening?
The more reactive metal will form a compound with the anion, and the other metal will be pulled out of solution and become a solid metal again.
Mg (s) + Zn(NO3)2 (aq) Mg(NO3)2 (aq)+ Zn(s)
A metal will not always replace a metal in a compound dissolved in water because of differing reactivity's.
An activity series can be used to predict if reactions will occur.
Double replacement reactionsoccur when ions exchange between two compounds. A precipitate, gas, or molecule will form.
This figure shows a generic double replacement equation.
The solid product produced during a chemical reaction in a solution is called a precipitate.
All double replacement reactions produce either water, a precipitate, or a gas.
This table shows the steps to write double replacement reactions.
This table summarizes different ways to predict the products of a chemical reaction.
1)Ca(OH)2 + Al2(SO4)3CaSO4 + Al(OH)3
2)Mg + Fe2O3Fe + MgO
3)C2H4+ O2CO2+ H2O
4)PbSO4PbSO3 + O2
Net Ionic Equations
Revisit course expectations
Check your grades to make sure they are accurate.
Homework for Chapter 8: 33-53 (odd) due Friday!
An aqueous solutioncontains one or more dissolved substances (called solutes) in water.
The solvent is the most plentiful substance in a solution.
Water is always the solvent in an aqueous solution.
There are many possible solutes—sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions.
Compounds that produce hydrogen ions in aqueous solutions are acids.
Ionic compounds can also be solutes in aqueous solutions.
When ionic compounds dissolve in water, their ions separate in a process called dissociation.
When two solutions that contain ions as solutes are combined, the ions might react.
If they react, it is always a double replacement reaction.
Three products can form: precipitates, water, or gases.
2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)
2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)
Ions that do not participate in a reaction are called spectator ionsand are not usually written in ionic equations.
2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)
Using solubility rules for ionic equations we can predict whether a precipitate is formed and thus predicting what the products are.
If the solubility rules predict insolubility we have a reaction, a precipitate!
Na2SO4 (aq) + BaNO3 (s) ???
Assume double replacement
Look at the products
NaSO4 + BaNO3 ???
Assume double replacement
Look at the products
Na2SO4 + Ba(NO3)2 2NaNO3 + Ba(SO4)
Write the complete ionic equation:
2Na+(aq) + SO42- (aq) + Ba2+ (aq) + 2NO3-(aq) 2Na+(aq) + 2NO3-(aq) + Ba(SO4)(s)
Eliminate all of the ions that did not change from the reactant side to the product side.
Ba2+ (aq) + SO42- (aq) Ba(SO4)(s) (net ionic eqn)
Problems of the day
Questions on homework.
Lab Write Up.
Lab write up!