conquer the Chemistry EOC: - PowerPoint Presentation

conquer the Chemistry EOC: Balancing Equations and Stoichiometry

Chemistry TEKS 8 (A) define and use the concept of a mole; 8 (B) use the mole concept to calculate the number of atoms, ions, or molecules in a sample of material; 8 (C) calculate percent composition and empirical and molecular formulas; 8 (D) use the law of conservation of mass to write and balance chemical equations; and 8 (E) perform stoichiometric calculations, including determination of mass relationships between reactants and products, calculation of limiting reagents, and percent yield.

IPC TEKS 7(C) demonstrate that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products; 7(D) analyze energy changes that accompany chemical reactions such as those occurring in heat packs, cold packs, and glow sticks and classify them as exothermic or endothermic reactions;

8 th TEKS 5(D) recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical formulas containing subscripts; 5(E) investigate how evidence of chemical reactions indicate that new substances with different properties are formed; and 5(F) recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the law of conservation of mass.

Label the Parts of an Equation

Why Balance Equations? Law of Conservation of Mass – Matter cannot be created or destroyed it can only change forms. In chemical reactions the number and mass of atoms on the reactant side of the equation must equal the number and mass of atoms on the product side of the equations.

Chemical Equations Recipe for a chemical reaction Relative number of reactants and products Coefficients represent the relative numbers. CH 4 + 2O 2  CO 2 + 2H 2 O

Law of Conservation of Matter: Balancing Chemical Equations Atoms are conserved in a chemical reaction. Coefficients are manipulated to balance chemical reactions and create equivalent measures. Identities cannot be changed. _ C 2 H 5 OH (l) + _ O 2 (g)  _ CO 2 (g) + _ H 2 O (g)

Balancing Chemical Equations C 2 H 5 OH (l) + O 2 (g)  CO 2 (g) + H 2 O (g) Count Atoms: Carbon 2 Carbon 1 Hydrogen 6 Hydrogen 2 Oxygen 3 Oxygen 3

Balancing Chemical Equations C 2 H 5 OH (l) + O 2 (g)  CO 2 (g) + H 2 O (g) C 2 H 5 OH (l) + 3 O 2 (g)  2 CO 2 (g) + 3 H 2 O (g)

Chemical Equations as Equivalents Coefficients from a balanced equation represent the number of theoretical mole equivalents and can be used in stoichiometric calculations.

8 th grade released question

Jelly Bean Equations and Chemical Equation Cards

Online Balancing Equation Practice http://sciencespot.net Click Kid Zone Click Matter & Atoms Go to: Balancing Equations Online Balancing Equations Online 2 http://funbasedlearning.com/chemistry/chemBalancer3/worksheet.htm

Balancing Equation Strips Draw a strip Balance the equation Write a word equation describing the reaction Make or demonstrate a representation of the equation

Chemical Reaction Types

Synthesis (Combination, Composition) Two or more substances combine to form a single substance. General equation: A + B  AB example: 2Na + Cl 2  2NaCl

Decomposition A compound is broken into two or more products. General equation: AB  A + B example: 2H 2 O 2H 2 + O2

Single Replacement A + BC  AC +B

Activity Series For an element to replace another the lone element must be more active than the element it is replacing in the substance. See the reference chart behind your periodic table.

Example: Zn+ 2 HCl  ZnCl 2 + H 2

Example: Thermite Reaction 2 Al + Fe 2 O 3  Al 2 O 3 + 2 Fe

Example: 2NaBr (aq) + Cl 2 (g) 2NaCl (aq) + Br 2 (g)

Double Replacement (Double Displacement) AB + CD  AD + CB

Double Replacement Reactions Occur in aqueous solutions For a DR reaction to occur one of the following must happen: A precipitate is formed (an insoluble or slightly soluble solid). A molecular compound (usually water is formed). A gas is formed. Follow Solubility Rules

Example: Production of a Precipitate Silver Nitrate + Sodium Chloride Precipitate AgCl (s)

Chemistry Released

Chemistry Released

Stoichiometry Dimensional Analysis The Mathematics of Chemistry

Stoichiometric Calculation Plan Write the chemical equation Balance the chemical equation Follow the steps of dimensional analysis Start with what is given Set up a series of equivalent measures End with your goal Solve the problem by cancelling units Record the appropriate answer with units

Stoichiometry Stoichiometry is a branch of chemistry that deals with the relative quantities of reactants and products in chemical reactions. Greek root words: Stoicheion meaning " element“ Metron meaning "measure"

What is Dimensional Analysis? Using the units, or dimensions , of measurements to express and calculate chemical quantities

What is the relationship? Dimensional analysis is a strategy used for doing stoichiometric calculations.

What are some common equivalent measurements? 1 inch =______centimeter(s) 1 week = ______ day(s) 60 seconds = ______minute(s) 1 lb =______ ounce(s) 1 cup = _____ fluid ounces 1 tablespoon = _____ teaspoon(s) 4 quarts = _____ gallon(s)

Common Equivalent Measurements 1 mile = _____ feet 1 kg = _____ 2.2 lb 1 ft = ____ inches 365 days = _____ year(s) 1 ton = _____ pounds

Dimensional Analysis –The Plan What is given? Start your calculation with this quantity with units. What is your goal? What you are solving for is your goal and should be on top of the last step of the problem. Set up a series of equivalent measures that cancels out all units except the goal units . 4. Solve the problem, and remember to mark through the cancelled units. 5. Record the appropriate answer with units.

Give it a try! How many seconds are there in 5.5 days? Follow the steps: What is given? 5.5 days What is your goal, and what are the units? Determine # of seconds in 5.5 days Set up a series of equivalent measure that cancels out all units except the goal units. Get started: **What fractions “ equal to 1 ” help transition from days to seconds?

Give it a try! 5.5 days X 24 hours X 60 minutes X 60 seconds = ? seconds 1 1 day 1 hour 1 minute 1 4.Record the appropriate answer with units.

What are some common equivalent measurements in chemistry? 1,000 g = _____kg 100 cm = ______ m 1 m = _____dm 1 L = _____ml 1 mole = _______ particles/atoms molar mass = _____ mole(s) Avogadro ’ s number = _____ mole(s)

Mole equivalents MOLE P A R T I C L E S G R A M S Avogadro ’ s Number Molar Mass

Molar Mass The mass in grams of 1 mole of the compound C 10 H 6 O 3 10 C = 10 X 12.011g = 120.11 6 H = 6 X 1.008g = 6.048 3 O = 3 X 15.999g = 48.997 TOTAL = *175.16 grams *Remember the significant figures rules.

Molar Mass The mass in grams of 1 mole of the compound calcium carbonate CaCO 3 Ca 1 X 40.078 grams = 40.078 grams C 1 X 12.011 grams = 12.011 grams O 3 X 15.999 grams = 47.997 grams TOTAL = *100.086 grams * Remember the significant figures rules.

Give it a try! How many grams are in 4.92 moles of calcium carbonate?

Stoichiometric Calculations – The Plan Write the chemical equation. Balance the chemical equation. *Follow steps to dimensional analysis: Start with what is given. Set up a series of equivalent measures. End with your goal. Solve the problem by cancelling units. Record the appropriate answer with units.

Give it a try! Stoichiometric Calculations 4.92 mol CaCO 3 X 100.086g CaCO 3 = 1 mol CaCO 3

Stoichiometry Basics Mole Ratios Measuring Moles The Mathematics of Chemistry Format Great Stoichiometry Relay Race Think, Pair, Share

Limiting Reactants for Recipes Stoichiometry  chocolate chip cookies Yum!!

Stoichiometric Calculations – The Plan Write the Chemical Equation. Balance the Chemical Equation. Follow steps to Dimensional Analysis: Start with what is given. Set up a series of equivalent measures. End with your goal. Solve the problem by cancelling units. Record the appropriate answer with units.

Stoichiometric Calculations – The Problem Lithium hydroxide is used in an outer space environment to remove excess exhaled carbon dioxide from the living environment. The products of the reaction are lithium carbonate and water. If 48.0 grams of lithium hydroxide are used in a small scale experimental device, how much carbon dioxide will the device process? The Plan: Write the chemical equation. Balance the chemical equation. Follow steps to dimensional analysis: Start with what is given. Set up a series of equivalent measures. End with your goal. Solve the problem by cancelling units. Record the appropriate answer with units. * Remember Significant Figures.

Stoichiometric Calculations – The Plan LiOH + CO 2 (g)  Li 2 CO 3 + H 2 O (g) 2. Balance the chemical equation. 1. Write the chemical equation. 2 LiOH + CO 2 (g)  Li 2 CO 3 + H 2 O (g)

Stoichiometric Calculations – The Plan 2 LiOH + CO 2 (g)  Li 2 CO 3 (g) + H 2 O (g) 48.0 g LiOH X 1 mole LiOH X 1 mole CO 2 X 44.009g CO 2 = 1 23.948 g LiOH 2 mole LiOH 1 mole CO 2 Follow steps to dimensional analysis:

Stoichiometric Calculations – The Answer When 48.0 grams of lithium hydroxide are available for use in a reaction, 44.1 grams of carbon dioxide can be processed by the reaction. *Remember the significant figures.

Write your own stoichiometry question for this reaction, and switch with your table partner: Barium chloride reacts with sodium sulfate in a precipitation reaction to make barium sulfate. Partner Share