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Understanding Chemical Reactions and Equations: A Comprehensive Guide

This guide provides an overview of chemical reactions, focusing on the writing of word and skeleton equations. It explains how reactants and products are represented, along with examples of synthesis, decomposition, single replacement, double replacement, and combustion reactions. The importance of balancing chemical equations to obey the law of conservation of mass is emphasized. Additionally, the role of catalysts in speeding up reactions without being consumed is discussed, offering insight into the fundamental principles of chemistry.

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Understanding Chemical Reactions and Equations: A Comprehensive Guide

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  1. CHEMICAL REACTIONS The process by which one or more substances are changed into one or more different substances

  2. Word Equations • To write a word equation, • Write the names of the reactants to the left of the arrow separated by plus signs; • Write the names of the products to the right of the arrow, also separated by plus signs. Reactant + Reactant  Product + Product

  3. EXAMPLE • Methane + Oxygen  Carbon dioxide + Water

  4. EXAMPLE 2 • Iron + Oxygen  Iron(III) Oxide

  5. EXAMPLE 3 Hydrogen Peroxide  Water and Oxygen catalase

  6. Skeleton Equations • Write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right. • A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products. • Here is the equation for rusting: • Fe + O2 Fe2O3

  7. Formula Writing Practice WS

  8. Catalyst • A catalyst is a substance that speeds up the reaction but is not used up in the reaction • Without catalyst With Catalyst

  9. Important Symbols

  10. Balancing Chemical Equations • To write a balanced chemical equation, • Write the skeleton equation • Use coefficients to balance the equation so that it obeys the law of conservation of mass. • Remember you want the same number of atoms of each element on each side of the equation.

  11. Example

  12. Example 2

  13. Example 3 -- Try on your own!!! • Write a balanced chemical equation for the reaction in which sodium hydroxide and calcium bromide react to produce solid calcium hydroxide and sodium bromide. (The reaction occurs in water.) NaOH(aq)+CaBr2(aq) Ca(OH)2(s)+NaBr(aq) 2NaOH(aq)+CaBr2(aq) Ca(OH)2(s)+2NaBr(aq)

  14. Summary

  15. Warm Up!! • _____NaClO3 →____ NaCl + __O2

  16. Chemical Equations from Names • Magnesium and Hydrogen Chloride produce Hydrogen and Magnesium Chloride • Calcium Hydroxide and Lithium Chloride produce Lithium Hydroxide and Calcium Chloride • Decompose Copper (II) oxide into Copper and Oxygen • Aluminum and Iron (III) oxide produce iron and aluminum oxide • combustion of Butane (C4H10) in air to produce carbon dioxide and water

  17. Warm Up • ___AgNO3 + __Ni  __Ni(NO3)2 + __Ag

  18. The Five Types of Reactions

  19. Chemistry with Synthesis Reactions A + B  AB

  20. 1. Synthesis Reactions (Combination) • Two or more reactants produce one product • Examples: NH3 + HCl  NH4Cl H2 + O2 H2O Ag + S  Ag2S Al + Cl2 AlCl3

  21. Chemistry with Decomposition Reactions AB  A + B

  22. 2. Decomposition • One reactant produces two or more products • Examples Ag2O Ag + O2 PCl5 PCl3 + Cl2 H2O2 H2O + O2 CuO Cu + O2

  23. Chemistry with Single Replacement AB + C  AC + B

  24. 3. Single Replacement • One element replaces another element • Must consult the activity series

  25. 3. Single Replacement • One element and one compound producing a different element and compound • Examples Fe + H3(PO4)  H2 + Fe3(PO4)2 H2 + CuO  Cu + H2O Zn + HCl  H2 + ZnCl2 Cl2 + KBr  Br2 + KCl

  26. Equations Activity Series Worksheet

  27. Chemistry with Double Replacement AB + CD  AD + CB

  28. 4. Double Replacement A double-replacement reaction is a chemical change involving an exchange of positive ions between two compounds. • Examples: Al(NO3)3 + NaOH  Al(OH)3 + NaNO3 PbCl2 + Li2SO4 PbSO4 + LiCl ZnBr2 + AgNO3 Zn(NO3)2 + AgBr BaCl2 + KIO3 Ba(IO3)2 + KCl

  29. 4. Double replacement • Three main products of a double replacement reaction • Precipitate (solubility table) • Water • Gas

  30. 5. Combustion • A combustion reaction • Chemical change • Element or a compound reacts with oxygen • Producing energy in the form of heat and light

  31. 5. Combustion A hydrocarbon reacts with oxygen to produce carbon dioxide and water Examples: CH4 + O2 CO2 + H2O C6H12O6 + O2 CO2 + H2O

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