Chemical Reactions Part II

Chemistry 1

Check for Understanding

Balance the following Chemical Equations:

CH4 + O2 CO2 + H2O

Na2O2 + H2SO4 Na2SO4 + H2O2

N2 + H2 NH3

When solid copper reacts with aqueous silver nitrate, the products are aqueous copper (II) nitrate and silver metal.

Review Individual Practice

Steps to Follow to Balance Equations

1. Determine the number of atoms for each element.

2. Pick an element that is not equal on both sides of the equation.

3. Add a coefficient in front of the formula with that element and adjust your counts.

4. Continue adding coefficients to get the same number of atoms of each element on each side.

**Note: LEAVE THE SUBSCRIPTS ALONE! (you cannot change the chemical formula to balance atoms)

Steps to Write Equations

1. When writing formulas don’t forget to look up charges if the compound is ionic!!!

2. Diatomic Molecules: Always travel in pairs1. H.O.F.Br.I.N.Cl. (Dr. HOFINBrCl)2. These elements need a subscript 2 after

them if they are by themselves!

3. Once the equation is written, then balance the equation by adding coefficients.

Individual Practice

Word problems:

When sodium metal reacts with iron (II) chloride, iron metal and sodium chloride are formed.

When dissolved beryllium chloride reacts with dissolved silver nitrate in water, aqueous beryllium nitrate and silver chloride powder are made. (include state)

On your homework from today write the names of the products and reactants for 1-6.

Types of Chemical Reactions

Types of Reactions DEMO Activity

LAB Pictures

Keys to success- Be sure your hand is VERY soapy!! Keep your hand flat Keep all your fingers together and “tuck your

thumb in” Do NOT move your hand once it is on fire. Do not forget to SMILE for your picture!

Synthesis Reaction

Synthesis Reaction: A reaction in which two or more substances combine to form a new compound.

A + B AB

Examples of Synthesis Rxn

A + B AB

Water: H2 + O2 H2O

Table Salt: Na + Cl2 NaCl

Given the following reactants, predict the products.

S8 + O2

Synthesis: 2Mg + O2 → 2MgO

Decomposition Reactions

Decomposition Reaction: A reaction in which a single compound breaks down to form two or more simpler substances.

AB A + B

Examples of Decomposition Rxn

Digestion is a series of decomposition reactions that break down food for fuel for your body.

The production of gasoline is done by “cracking” crude oil where you break down carbon and hydrogen molecules.

Electrolysis of water:

H2O H2 + O2

Decomposition: C12H22O11 → 12C + 11H2O

Combustion Reactions

Combustion Reactions: A reaction where an organic molecule is combined with oxygen.

CxHy + O2 CO2 + H2O

Oxygen (O2) is a reactant.

CO2 and H2O are produced

Uses for Combustion

Combustion reactions are used in your home everyday in stoves, water heaters, and furnaces.

Example of Combustion Reaction:

2CH4 + 4O2 2CO2 + 4H2O

Combustion: CH4 + 2O2 → CO2 + 2H2O

Single Displacement Reaction

Single Displacement Reaction: A reaction in which one element takes the place of another element in a compound.

* A more reactive element will take the place of a less reactive element. (see page 286 Table 3)

AX + B BX + A

Examples of Single Displacement

Zn + HCl ZnCl2 + H2

Q: In the example above, which element is more reactive?

CuCl2 + Al

Q: In the above example, predict the products.

Single Replacement: Cu + 2AgNO3 → Cu(NO3)2 + 2Ag

Double Displacement Reaction

Double Displacement Reaction: A reaction where there is an apparent exchange of atoms or ions between two compounds.

AX + BY AY + BX

Indicators of a double displacement reaction:

Formation of a Precipitate (solid)

Formation of a Gas (bubbles)

Formation of Water

Example of Double Displacement

The yellow lines on the roads are made from a double displacement reaction.

Pb(NO3)2 + K2CrO4 PbCrO4 + KNO3

Double Replacement: 3CuCl2 + 2Na3PO4 → Cu3(PO4)2 + 6NaCl

Practice (in your notes)

Balance and Classify the following chemical reactions: __Mg + ___HCl ____MgCl2 + ____H2

__C4H8 + ___ O2 ____CO2 + ____ H2O

___Ca(OH) 2 + ___H2 SO4 ____CaSO4 + ___H2O

___N2 + ___O2 ____N2O5

Individual Practice

Unit 8 Review Packet

Access Term 1 Final Exam Review Packet (blog)

Questions? (10minutes)

Chemical Equations/Reactions Exam

Friday, March 6th!

Term deadline is March 9th!

Acid-Base Reactions

Acid/Base Rxn: The reactants will include an acid combining with a base. The products will include water and a salt.

HX + B(OH) H2O + BX

Acid-Base Reactions

The Bronsted-Lowry Definitions

Acid is a proton donor.

Base is a proton acceptor.

An acid-base reaction is often called a neutralization reaction.

Examples of Acid/Base Reaction

HCl + Ca(OH)2 H2O + CaCl2

HCN + K(OH) H2O + KCN

Oxidation Reduction (REDOX) Reactions

Reactions in which one or more electrons are transferred (redox reactions)

Example: H2(g) + Cl2(g) 2HCl(g)

Electrons are transferred from the hydrogen to the chlorine.

Recall Rules for Assigning Oxidation States

Remember: The sum of the oxidation states in a neutral compound must equal zero.

Oxidation States

Assign oxidation states to each of the atoms in the following compounds:

Hint: Check that oxidation states sum up to the charge on the compound/ion.

CaF2

C2H6

H2O

ICl5

KMnO4

SO42-

Practice- Oxidation States

Fe2O3 + 2Al Al2O3 + 2Fe

THE IRON GAINED ELECTRONS. IT HAS BEEN REDUCED.

THE ALUMINUM LOST ELECTRONS. IT HAS BEEN OXIDIZED.

OIL – Oxidation Involves Loss (of electrons)

RIG- Reduction Involves Gain (of electrons)

OIL RIG Practice

For each reaction, identify the atoms that undergo reduction or oxidation (and charges). Also, list the oxidizing and reducing agents.

2H2(g) + O2(g) 2H2O(g)

Zn(s) + Cu2+(aq) Zn2+

(aq) + Cu(s)

2AgCl(s) + H2(g) 2H+(aq) + 2Ag(s) + 2Cl-(aq)