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CHEMICAL REACTIONS

Learn about chemical reactions and how to write word equations, skeleton equations, and balanced chemical equations. Explore different types of reactions like synthesis, decomposition, single replacement, double replacement, and combustion.

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CHEMICAL REACTIONS

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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, 1. write the names of the reactants to the left of the arrow separated by plus signs; 2. 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

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

  8. Important Symbols

  9. 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.

  10. Example

  11. Example 2

  12. 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.

  13. Summary

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

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

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

  17. 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

  18. 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

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

  20. Combustion • A combustion reaction • chemical change • element or a compound reacts with oxygen • producing energy in the form of heat and light

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

  22. 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

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