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Unit 2 Exam Review

Unit 2 Exam Review. BBC Clip. Death Penalty Reading. Unit 3 Theme – Why does the same chemical both help and Hurt me?. Balancing Equations Exploration. With your partner, complete the simulator on the computer Complete the entire handout. Be sure to defend your reasoning!.

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Unit 2 Exam Review

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  1. Unit 2 Exam Review

  2. BBC Clip

  3. Death Penalty Reading

  4. Unit 3 Theme – Why does the same chemical both help and Hurt me?

  5. Balancing Equations Exploration • With your partner, complete the simulator on the computer • Complete the entire handout. Be sure to defend your reasoning!

  6. Balancing Chemical Equations and Types of Chemical Reactions

  7. Parts of a Chemical Reaction Cu (s) + 2 AgNO3 (aq) → Cu(NO3)2 (aq) + 2 Ag (s) Reactants Products Letters in parentheses show the state of matter. Coefficients (numbers) in front of a chemical formula show “how many.” The arrow separates the reactants and products.

  8. Balancing a Chemical Reaction Equation • Atoms are not createdor destroyedduring a chemical reaction. • Scientist know that there must be the samenumber of atoms on each sideof the arrow.

  9. Is it balanced? __Cu + __ AgNO3 → __Cu(NO3)2 + __ Ag Cu = Cu = Ag = Ag = NO3 = NO3 =

  10. Balancing a Chemical Reaction Equation • To balance the chemical equation, you must add coefficientsto the different parts of the equation. Cu (s) + 2 AgNO3 (aq) → Cu(NO3)2 (aq) + 2 Ag (s)

  11. Steps for Balancing Chemical Reaction Equations • Determine number of atoms for each element for the reactants and products separately. • Try to add coefficients to the equation to get the same number of atoms on each side. • Note: Coefficients multiply the atoms in the compound. Keep the compound formulas the same. Do not change subscripts. • Hint: Balance anything that is not hydrogen or oxygen first. Then balance hydrogen. Balance oxygen last.

  12. + H2 O2  H2O (g) (g) (l) O O O H H H H H H O H H Law of Conservation of Mass • Matter cannot be created or destroyed in a chemical reaction • The number of atoms on the reactant side must equal the atoms of the products Unbalanced! Balanced!

  13. Balanced Chemical Equations • A chemical equation is “balanced” when there are the same number of atoms of each element on both sides of the arrow. NaHCO3 (s) + HC2H3O2 (aq) èNaC2H3O2 (aq) + CO2 (g) + H2O (l) Is it balanced?

  14. Is it balanced? Practice • Determine the number of atoms of each element in the reactants and products. Then, state whether the equation is balanced. • P4 + O2 → P2O5 • C3H8 + O2 → CO2 + H2O • Ca2Si + Cl2 → CaCl2 + SiCl4 • Si + CO2 → SiC + SiO2 Not balanced. Not balanced. Not balanced. Not balanced.

  15. coefficient + H2 O2  H2O (g) (g) (l) Balancing Equations 2 2 • Only the coefficients can be changed! H = O = 2 4 H = O = 2 4 2 1 2

  16. Balancing Tips • Always balance non-Oxygen’s & Hydrogen’s first (ex. Chlorine) • Then balance Hydrogens • Balance Oxygens Last

  17. Balancing Practice! P4 + O2 → P2O5 P4 + 5 O2 → 2 P2O5 Ca2Si + Cl2 → CaCl2 + SiCl4 Ca2Si + 4 Cl2 → 2 CaCl2 + SiCl4 Si + CO2 → SiC + SiO2 2 Si + CO2 → SiC + SiO2 C3H8 + O2 → CO2 + H2O C3H8 + 5 O2 → 3 CO2 + 4 H2O

  18. Overview of Major Chemical Reaction Types • Synthesis • Decomposition • Single-Replacement • Double-Replacement • Combustion

  19. + 2H2 O2  2H2O (g) (g) (l) H H O O H H H H H H 1. Synthesis Reactions • Two substances combine to make one • Synthesismeans “to make” O O

  20. A + B  AB SYNTHESIS Na + Cl2 NaCl

  21. NH3 (l) N2 + H2  (g) (g) 2. Decomposition Reactions • One substance breaks down into 2 • Decompositionmeans “to break down” or “decay” H H H H N N H H

  22. AB  A + B Decomposition NaCl  Na + Cl2

  23. one element replaces another in a compound 3. SINGLE REPLACEMENT AB + C  AC + B

  24. Single Replacement Reaction

  25. Single Replacement AB + C  AC + B or CB + A NaBr + Cl2 NaCl + Br2

  26. 4. DOUBLE REPLACEMENT Both elements in two compounds switch places AB + CD  AD + CB

  27. Double Replacement NaBr + Pb2S3 Na2S + PbBr3 K2SO4 + Ba(OH)2 KOH + BaSO4

  28. CH4 C2H4 + + O2 O2 CO2 CO2 + + H2O H2O   C6H12O6 + O2 CO2 + H2O  5. Combustion Reactions • A hydrocarbon reacts with oxygen gas to produce carbon dioxide and water vapor • Combustionmeans to “burn in oxygen”

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