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Chemical Reactions

Chemical Reactions. Types of Reactions. Types of Reactions. Combination reactions Decomposition reactions Displacement reactions Precipitation reactions You need to be able to identify each type. A. Combination. the combination of 2 or more substances to form a compound

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Chemical Reactions

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  1. Chemical Reactions Types of Reactions

  2. Types of Reactions • Combination reactions • Decomposition reactions • Displacement reactions • Precipitation reactions You need to be able to identify each type.

  3. A. Combination • the combination of 2 or more substances to form a compound • only one product forms A+ BAB 2P + 3Br2 2PBr3

  4. E.g. Combination Reaction

  5. B. Decomposition • a compound breaks down into 2 or more simpler substances • only one reactant ABA+B 2H2O2 2H2O + O2

  6. E.g. Decomposition Reaction

  7. C. Displacement • one element replaces another in a compound • metal replaces metal (+) • nonmetal replaces nonmetal (-) A +BCAC+B Zn + 2HCl  ZnCl2 + H2

  8. E.g. Displacement Reaction

  9. D. Precipitation • ions in two compounds “change partners” • cation(+) of one compound combines with anion(-) of the other AB +CDAD +CB 2KOH + CuSO4 K2SO4 + Cu(OH)2

  10. Exchange Reactions • Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together • Example: AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq) • Another example: K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s) 2

  11. Precipitation

  12. Predicting the products • 1) Identify the likely reaction type based on the reactants: • Combination - often 2 elements • Decomposition - 1 compound • Displacement - 1 compound & 1 element • Precipitation - 2 compounds

  13. Predicting the products • 2) Use the information in your notes about likely products to help you determine the products • Combination- put the 2 elements together-look at the charges and use the crisscross method • Decomposition- pull the compound apart- for us, it will usually be the 2 elements that make up the compound • Pay attention to the diatomics

  14. Predicting Products • 2) continued • Displacement- look at the activity series to see if the element can replace one of the elements in the compound • If the reaction occurs, find the charges of the each of the elements. • Trade the places of the metals • Write the new formula of the compound using the crisscross method • Eliminate the charge from the new lone element and write it alone.

  15. Predicting products • 2) Continued • Exchange - trade the cations of the compounds • Pay attention to charge of your ions and use the crisscross method to write the formula. • Look at your solubility table on the back of your periodic table to determine which product is solid (the insoluble one is the solid) and which is aqueous • Be sure to indicate state of matter for every compound in exchange reactions • If both are aqueous (soluble), no reaction occurs. • Water is a liquid

  16. Predicting Products • 3) Balance the equation.

  17. Practicing exchange reactions • Predict the products. • HCl(aq) + AgNO3(aq)  • Pb(NO3)2(aq) + BaCl2(aq)  • FeCl3(aq) + NaOH(aq)  • KOH(aq) + CuSO4(aq)  AgCl(s)+ HNO3(aq) PbCl2(s)+Ba(NO3)2(aq) 3 3 Fe(OH)3(s) + NaCl(aq) 2 K2SO4(aq) + Cu(OH)2(s)

  18. Mixed Practice • State the type & predict the products. • BaCl2 (aq)+ H2SO4(aq) • Zn(s) + CuSO4(aq)  • Cs(s) + Br2 (l) • FeCO3(s) 

  19. Exchange reaction 2 BaSO4(s) + HCl(aq) BaCl2(aq) +H2SO4(aq) • What you would see: • Two solutions are mixed and a white solid (precipitate) forms on mixing

  20. Displacement reaction ZnSO4(aq) + Cu(s) Zn(s) + CuSO4(aq)  • What you would see: • Copper sulfate solution fades in colour…gets less blue • Zinc metal disappears as it reacts • Brown/orange copper metal appears

  21. Combination reaction 2 2 CsBr(s) Cs(s) + Br2 (l) • What you would see: • Explosion…lots of energy given off …Cs is a group one metal! • Brown/red bromine liquid would disappear quickly as it reacts • Silvery Cs metal would quicklydisappear as it reacts • A white crystalline solid is left behind

  22. Decomposition reaction • FeCO3(s)  FeO (s) + CO2(g) • What you would see: • You would need to heat this for the reaction to take place • green powder turns black • gas given off could be bubbled through limewater to test for carbon dioxide

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