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Chemical Reactions 7.1 SKIP MOLES.

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1 Chemical Reactions 7.1 SKIP MOLES

2 Avogadro's number is 6.02 x 1023 which is about a mole
True False Statement Products are on the left, and yield reactants on the right of a chemical equation Law of conservation of mass says that matter (elements) cannot be created or destroyed When balancing equations you CAN change the subscripts, but NOT the coefficients Avogadro's number is 6.02 x 1023 which is about a mole Cu + O CuO Is balanced

3 Chemical Reactions Chemical reactions change substances into new substances with new chemical and physical properties Ways to know a chemical reaction is occurring: A release of gas A color change Production of light and/or heat The production of a precipitate (solid)

4 Parts of Chemical Reactions
The Law of Conservation of Mass States that no matter can be created nor destroyed in a chemical reaction # on the left = # on the right

5 Two parts of a chemical reaction
Reactants: a substance or molecule that participates in a chemical reaction Usually found on the left side of an equation Products: a substance that is formed in a chemical reaction Usually found on the right side of an equation

6 Parts of a chemical equation
2 H2 + O2  2 H2O Atoms are rearranged in chemical reactions to make new substances by making or breaking bonds. Coefficient Subscript Products Reactants

7 Chemical Equations Chemical equation:
A representation of a chemical reaction that uses symbols to show the relationship between the reactants and products CH O  CO H2O

8 When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction, but you may NOT change the subscripts. Changing the subscripts changes the compound!! Subscripts are determined by the valence electrons (charges for ionic or sharing for covalent)

9 The subscripts tell you how many atoms of a particular element are in a compound.
The coefficient tells you about the quantity, or number, of molecules of the compound

10 1. Write the correct formula for the reactants and the products.
2. Find the number of atoms for each element on the left side. Compare those against the number of the atoms of the same element on the right side. 3. Determine where to place coefficients in front of formulas so that the left side has the same number of atoms as the right side for EACH element 4. Check your answer to see if: The numbers of atoms on both sides of the equation are now balanced. The coefficients are in the lowest possible whole number ratios. (reduced)


12 Magnesium + Oxygen (air)  Magnesium Oxide Mg + O2 MgO 1 Mg 1 Mg
Write the equation that describes the burning of magnesium in air to form magnesium oxide. Magnesium + Oxygen (air)  Magnesium Oxide Mg O MgO 1 Mg Mg 2 O O 2 2 2 Balanced!

13 Potassium metal reacts violently with water to produce potassium hydroxide and hydrogen gas.
Potassium + Water  Potassium Hydroxide + Hydrogen Gas

14 Math Practice pg 195 1. Balance the production of hydrogen chloride from hydrogen and chlorine

15 Math Practice Balance H2O H2O + O2 Mg + HCL H MgCl2

16 Math Practice Ethylene, C2H4 burns in the presence of oxygen to produce carbon dioxide and water vapor. Balance.

17 Moles (Mol) is the amount of subatnce that contains about 6.02 x particles of that substance. Called Avagardo’s # Usually atoms, ions, or molecules Molar mass- mass of 1 mole of a substance

18 Types of Reactions Ch. 7.2

19 Combustion reactions always yield heat, light and water
True False Statement A synthesis reaction is when a compound breaks down into 2 or more elements In single replacement 1 pair switches places, and usually has 2 compounds on both sides Combustion reactions always yield heat, light and water Oxidation reactions gain electrons, while reduction lose electrons AB A + B Is decomposition

20 Types of reactions 5 Types of Reactions Synthesis Single Double
Decomposition Combustion

21 Synthesis Synthesis Reaction: A reaction in which two or more substances combine to form a new compound A + B  AB Example: 2Na + Cl2  2NaCl

22 Decomposition AB  A + B Example: 2H2O  2H2 + O2
Decomposition Reaction: A reaction in which a single compound breaks down to form two or more simpler compounds. AB  A + B Example: 2H2O  2H2 + O2

23 Single Displacement AX + B  BX + A
Single-Displacement Reaction: A reaction in which one element or radical takes the place of another element or radical in a compound AX + B  BX A Example: 3 CuCl2 + 2Al  2AlCl Cu

24 Double Displacement AX + BY  AY + BX
Double-Displacement Reactions: A reaction in which a gas, solid, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds AX BY  AY BX Pb(NO3)2 + K2CrO4  PbCrO K2 NO3

25 Combustion Combustion Reaction: The oxidation of an organic compound in which heat is released Also known as “burning” Always contain a hydrocarbon and oxygen from the air as reactants Always produce carbon dioxide, water, and heat CH4 + 2O2 → CO2 + 2H2O + heat

26 Lose Electrons = Oxidation Gain Electrons = Reduction
LEO says GER!!! Electrons are sometimes transferred in chemical reactions These reactions are called oxidation- reduction reactions (REDOX reactions) Oxidation Substances that lose electrons are oxidized Reduction Substances that accept electrons are reduced LEO- Lose Electrons = Oxidation GER- Gain Electrons = Reduction

27 Oxidation or Reduction?
Fe changes to Fe oxidation Pb4+ changes to Pb reduction F changes to F reduction Cr2+ changes to Cr oxidation Mg2+ changes to Mg reduction

28 Energy Change and reaction rates

29 Increasing temperature speeds up the reaction rate
True False Statement Endothermic releases energy/forms bonds, while exothermic absorbs energy/breaks bonds Increasing temperature speeds up the reaction rate The smaller the surface area and concentration, that faster the reaction rate A catalyst is a substance that speeds up a reaction without being consumed Reaction rate, is the rate at which products turn into reactants

30 Energy is released or absorbed
Endothermic Reaction Exothermic Reaction Absorbs energy Energy is required to break bonds Releases energy Energy is greater than energy needed to break bonds

31 Conservation of Energy
Energy is not created or destroyed in endothermic and exothermic reactions Total energy at beginning = total energy at end

32 Reaction Rate Rate at which reactants change into products over time
How fast reactants are being consumed How fast the products are being formed How fast energy is absorbed or released

33 Factors Affecting Reaction Rate
Temperature in temp= in rate Faster particles Slower particles Surface Area in S.A= in rate More collisions

34 Factors Affecting Reaction Rate
Stirring collisions= in rate Ex: Washing machine Concentration # of particles in a given volume in conc.= in rate in pressure= in rate gases

35 Factors Affecting Reaction Rate
Catalyst Affects substance w/out being used up Speeds up reaction Written over yield arrow

36 Equilibrium Ch 7.5

37 Means an equation is reversible/at equilibrium
True False Statement Means an equation is reversible/at equilibrium Equilibrium means the forward and reverse paths of the reaction take place at the same rate There are 3 types of equilibrium-chemical, physical and atomic La Chatelier said when a change is introduced, the equation will do the opposite Temperature, pressure, and concentration affect equilibrium

38 Equilibrium State in which the forward and reverse paths of change take place at the same rate Physical and Chemical

39 Types of Equilibrium Physical Chemical Opposing physical change takes place at the same time Opposing chemical changes take place at the same time

40 La Chatelier’s Principle
When a change is introduced to a system in equilibrium, the equilibrium shifts in the direction that relieves the change

41 Factors Affecting Equilibrium
Temperature in temp will shift in the direction that removes heat from the system Pressure in pressure will shift in the direction that decreases the pressure of the system

42 Factors Affecting Equilibrium
Concentration Equilibrium will shift in direction that produces concentration

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