Chemical reactions

We will be talking about the following types of reaction? Precipitation Oxidation Decomposition and synthesis Acid-base neutralization reaction

The goal To balance a chemical equation Represent a precipitation reaction use a molecular model Identify oxidation reaction and understand how they function Associate known chemical reactions with decomposition or synthesis reactions. Recognize an acid base chemical reaction based on its equation Determine the molecular formula of the salt formed during an acid and base neutralization reaction. Determine the quantity of reagents and products in a reaction.

Chemical equations Reactants products Atoms cannot be destroyed or created The exact atoms that appear on the left, must appear on the right.

1.Balancing equations Write down all the atoms, grouped by molecule for the reactant Write down all the atoms, grouped by molecule for the products Begin trying to balance everything, remember you must multiply whole molecules

Examples H2SO4 + NaOH H2O + Na2SO4

Al + HCl H2 + AlCl3

NH3 + O2 NO + H2O

Tips and Tricks PRACTICE Start with elements that appear only once on each side Leave elements to the end Remember lowest common multiples (LCM’s) If the element is odd on one side and even on the other , multiply the odd side by 2 PRACTICE

C6H12O6 + O2 CO2 + H2O

Fe + Cl2 → FeCl3

TiCl4 + H2O → TiO2 + HCl

Ba3N2 + H2O → Ba(OH)2 + NH3

Extra sheet up front

2.Precipitation reactions A reaction where a precipitate forms after two aqueous solutions are mixed together. Precipitate: A solid that falls out of a liquid.

2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq)

Represent the following reactions using the particle model AgNO3 (aq) + KCl (aq) → AgCl (s) + KNO3(aq) BaCl2(aq) + K2SO4(aq)  BaSO4(s) + 2 KCl(aq) CuSO4(aq) + 2NaOH(aq) → Na2SO4(aq) + Cu(OH)2(s)

Exam type question Represent the following reaction using the particle theory. Silver nitrate is mixed with sodium bromide to produce a strong electrolyte and silver bromide which is slightly soluble.

Exam type question Represent the following reaction using the particle theory. Mixing of two strong electrolytes produces a precipitate of Alumimun hydroxide in a sodium chloride solution.

Exam type question Represent the following reaction using the particle theory. Mixing of two strong electrolytes produces a precipitate of Calcium sulphate in a lithium nitrate solution.

Represent the following reaction using the particle theory Represent the following reaction using the particle theory. Silver nitrate is mixed with sodium bromide to produce a strong electrolyte and silver bromide which is slightly soluble.

3. Oxidation reaction Also known as a combustion(burning) reaction A reaction in which oxygen gas(O2) is a reactant. Always produces heat.

Fe (s) + O2Fe2O3

2 Cu + H2O +CO2 + O2  Cu(OH)2 + CuCO3

C6H12O6 + 6 O2 = 6 CO2 6 H2O

Respiration C6H12O6 + 6O2 → 6CO2 + 6H2O 

Ethanol (C2H5O) burns with oxygen to create water and carbon dioxide Ethanol (C2H5O) burns with oxygen to create water and carbon dioxide. Write the balanced equation for this reaction.

Propane(C3H8) burns to produce carbon dioxide and water Propane(C3H8) burns to produce carbon dioxide and water. Write the balance equation

Acetylene (C2H2) is oxidized to produce carbon dioxide and water Acetylene (C2H2) is oxidized to produce carbon dioxide and water. Write the balanced equation.

Hydrogen gas undergoes oxidation to produce water Hydrogen gas undergoes oxidation to produce water. Write the balance chemical reaction.

P285 # 3

4. Decomposition and synthesis A decomposition reaction is the breakdown of a compound into two or more components. AB  A + B Example: Hydrolysis of water 2 H2O(l)  2H2(g) + O2(g)

Synthesis Synthesis is a chemical reaction in which elements or compounds combine to produce one or more complex compounds. A + B  AB Example: O2(g) + H2(g)  H2O N2(g) + H2(g)  NH3(g)

Is the following reaction synthesis or decomposition? Why? Respiration C6H12O6(s) + 6O2  6CO2 + 6H2O

Is the following reaction synthesis or decomposition? Why? Photosynthesis 6CO2 + 6H2O  C6H12O6(s) + 6O2

Is the following reaction synthesis or decomposition? Why?

Digestion Your body takes complex molecules, such as complex sugars, protein, and fats and break them down into simpler molecules Breakdown of lactose C12H22O11+H2O→C6H12O6+C6H12O6+ heat.

Breakdown of proteins

worksheet P. 287 #4

5+ 6 Acid Base Neutralization equations Acid-base neutralization is a chemical reaction that occurs when an acid and a base are mixed together. The products are a salt and water. Acid + base salt + water The pH becomes 7

Acid Base Neutralization equations Acid + base salt + water Steps Write the dissociation equation Find your water ( H+ and OH-) Put the other ions together to form a salt

Write the dissociation equations for the following NH4OH KOH Ca(OH)2 Al(OH)3

practice KOH + H2SO4 HCl + Ca(OH)2 NaOH + CH3COOH

Q. 6.15, 6.16 p635

Salt A salt is an electrolyte composed of a cation and anion that are not H+ or OH-. It generally has a pH of 7 when dissolved in water.

7. Stoichiometry The coefficients in a balanced equation give the stoichiometry of the equation It tells you how many molecules of one type react with the other type and how many molecules they produce

Stoichiometric calculations By knowing how much of one compound is used or produced, you can determine the amounts for the rest of the equation Possible because of conservation of mass and stoichiometric relations

Steps Read the question Balance the equation Set-up cross multiplication Top line – from the question Bottom line – from the equation

The Cross Multiplication Top line An x from your question (moles or grams) The moles or grams mentioned in the word problem Bottom line If top line is moles, only coefficient If top line is grams, coefficient and molar mass

3 types Mass to mass Mass to moles Moles to moles Solve them all the same way

Examples moles-moles Calculate the number of moles O2 needed to burn 10 moles of methane. CH4 + O2 CO2 + H2O

Example moles - grams Calculate how many grams of methane must be burnt with oxygen to produce 3 moles of CO2.

Example mass-mass Using the following equation how much copper could be extracted from 900g of copper (II) oxide? 3 CuO + 2NH3 N2 + 3Cu + 3H2O

How many grams of sodium sulfate will be formed if you start with 200 grams of sodium hydroxide and you have an excess of sulfuric acid? 2 NaOH + H2SO4  2 H2O + Na2SO4

How many grams of lithium nitrate will be needed to make 250 grams of lithium sulfate, assuming that you have an adequate amount of lead (IV) sulfate to do the reaction? Pb(SO4)2 + 4 LiNO3  Pb(NO3)4 + 2 Li2SO4

6.5, 6.6 622 6.7,6.8 623 6.9, 6.10 626 6.11, 6.12 627 6.13, 6.14 629