© 2005 mark s. davis ap chemistry chapter 3. © 2005 mark s. davis law of conservation of mass mass...

© 2005 Mark S. Davis

AP CHEMISTRY

Chapter 3


Law of Conservation of Mass

• Mass is neither created nor destroyed in chemical reactions– Lavoisier


Chemical equations

• Tell you: – What has – What – Ratio of – Products, reactants– Conditions


Generally

• Reactants Products

• Coefficients


Symbols

• (s)

• (l)

• (g)

• (aq)• +


Example

• Carbon is burned in air to form carbon dioxide

•


Example

• Carbon is burned in air to form carbon monoxide

• 2 2


Balancing equations

• Why?– To show conservation of mass– Keep proper amounts of reactants and

products– Show proper ratios between products

and reactants


Example

C2H6 + O2 CO2 + H2O


Patterns of reactivity

• Groups are similar in reactivity

• Alkali metals


Types of reactions

• Combustion

• Synthesis (Combination)

• Decomposition

• Single Replacement

• Double Replacement


Combustion Reaction


Combustion

• Occurs in air

•

•


Combustion Reactions

• Fuel – Carbon compound

• Ignition source – flame

• Oxygen source


Synthesis Reaction

• Reaction of two substances to form one product

• Either elements or compounds react to form one compound as product

• Generally:


Example

Mg + O2 MgO

Sodium reacts with Chlorine


Decomposition Reaction

• One compound breaks apart to form two or more other elements or compounds.

• Generally:

• Sodium azide


Airbags


Example

NaN3(s) Na(s) + N2(g)

Sugar is decomposed to form carbon and water


Single Replacement

• Reaction of an element and a compound to form two new substances

• Generally:

• Zinc and Copper sulfate


Example

Zn(s) + CuSO4(aq)


Solubility Rules

• In the book… table 4.1 p 111

• Also posted online.


Double Replacement

• Two solutions react to form two or more new substances

• Generally:

• Lead (II) nitrate and potassium iodide

• Identify the solid, gas, liquid, aqueous components


Example

Pb(NO3)2(aq) + KI(aq)


• http://dbhs.wvusd.k12.ca.us/webdocs/ChemTeamIndex.html

• http://dbhs.wvusd.k12.ca.us/webdocs/Equations/Equations.html


Atomic Weights

• The weight of an atom of an element


Average Atomic Mass

• Average mass of all the isotopes of an element– 98.5% C-12– 1.5% C-13


Formula Weight

• The sum of the masses of all the atoms in a compound.

• Usually refers to – –


Molecular Weight

• The weight of all the atoms in a – –


The MOLE

• Quantity of a substance


Molar Mass

• The mass in grams of one mole of a substance– –


Avogadro’s Number

• The number of particles in one mole of a compound

• 6.022 x 1023 particles in one mole


Conversions


Empirical Formulas

• Simplest formula

• C6H12O6 can be reduced to

• Represents the


Empirical Formulas

• Ethylene glycol, the substance used in automobile antifreeze, is composed of 38.7% C, 9.7% H, and 51.6% O by mass. Its molar mass is 62.1 g/mol. What is the empirical formula? What is the molecular formula?


Empirical Formulas• Caproic acid, which is responsible

for the foul odor of dirty socks, is composed of C, H, O. Combustion of 0.225 g of caproic acid produces 0.512 g CO2 and 0.209 g H2O. What is the empirical formula of caproic acid? If it has a molar mass of 116 g/mol, what is the molecular formula?


Problem

• Determine the empirical formula of a compound that has the composition of 20.20 % magnesium, 26.60 % sulfur, 53.20 % oxygen.


Problem 2

• It was determined that a compound was made from 43.66 % P and 56.34 % O, what is the empirical formula?


Molecular Formulas

• Represents the formula of the actual molecule

• If the empirical formula is CH2O and the molar mass is 120 amu, what is the molecular formula?


Early Stoichiometry

• Stoichiometry Steps for success online

• Method of converting


Limiting Reactants


Theoretical Yield

© 2005 mark s. davis ap chemistry chapter 3. © 2005 mark s. davis law of conservation of mass mass...

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empirical formulascaproic

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carbon monoxide

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