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Chemical Reactions & Chemical Equations

CHEM 106. Chemical Reactions & Chemical Equations. Dr. Ron Rusay. The Reaction of Sodium & Chlorine. http://chemconnections.org/general/movies/NaCl-form.MOV. General Chemical Reactions.

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Chemical Reactions & Chemical Equations

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  1. CHEM 106 Chemical Reactions & Chemical Equations Dr. Ron Rusay

  2. The Reaction of Sodium & Chlorine http://chemconnections.org/general/movies/NaCl-form.MOV

  3. General Chemical Reactions • Any chemical reaction can be described as a molecular or atomic change. It produces one or more observable changes. • e.g. color change, gas bubbles, heat, etc. • Reactions are generally described as Reactant(s) Product(s) • The reaction is written as a chemical equation with chemical formulas: 2 Na + Cl2 2 NaCl

  4. Chemical Equations • Chemical equations describe the change(s) in Reactant(s) to Product(s) including physical state(s). • Notations: (g), (l), (s), (aq) • 2 Na (s) + Cl2(g) 2 NaCl (s) • Others: arrows for gas ( ) and solid ( )  for heat, for reversibility (equilibrium)

  5. Types of Chemical Reactions • Combination (Synthesis) • Decomposition • Single Displacement • Double Displacement • Combustion • Others: Precipitation, Oxidation-Reduction, Neutralization

  6. Types of Chemical Reactions • Combination (Synthesis) • Decomposition • Single Displacement • Double Displacement • Combustion • Others: Precipitation, Oxidation-Reduction, Neutralization

  7. General Chemical Reactions http://chemconnections.org/general/movies/rxn-types.mov

  8. Chemical Reactions • Combination (Synthesis) • A + B C • Example: • H2 (g) + O2 (g) H2O (g) • Balancing (Conservation of Atoms): • H2 (g) + O2 (g) 2 H2O (g) • Stoichiometry: • https://www.youtube.com/watch?v=hSBT6oe6dSA&index=5&list=PLA3383CE72437FC43

  9. Synthesis of Water http://chemconnections.org/general/movies/H2O-form.MOV Three Balloons: https://www.youtube.com/watch?v=a6qGIMqDKwA&index=4&list=PLA3383CE72437FC43

  10. An Unwanted Synthesis of WaterCombustion & the Hindenburg 1937 http://chemconnections.org/general/movies/qthiburg.mov

  11. QUESTION • The electrolysis of water is the reverse of the synthesis of water. Which equation best represents the change that takes place when water is electrolyzed? • A) H2O(l) → H2O(g) • B) H2O(g) → H2O(l) • C) 2 H2O(l) → 2 H2(g) + O2(g) • D) 2 H2(g) + O2(g) → 2 H2O(l)

  12. Answer • The electrolysis of water is the reverse of the synthesis of water. Which equation best represents the change that takes place when water is electrolyzed? • A) H2O(l) → H2O(g) • B) H2O(g) → H2O(l) • C) 2 H2O(l) → 2 H2(g) + O2(g) • D) 2 H2(g) + O2(g) → 2 H2O(l)

  13. Chemical Reactions https://phet.colorado.edu/sims/html/balancing-chemical-equations/latest/balancing-chemical-equations_en.html • Decomposition • A B + C • 2 NI3 (s) N2 (g) + 3 I2 (s) http://chemconnections.org/general/movies/NI3-decomp.MOV

  14. QUESTION Ammonium nitrate, when heated, decomposes into nitrogen gas, oxygen gas, and water vapor. It may be explosive. What is the sum of the coefficients in the balanced equation using smallest integer coefficients? A) 3 B) 5 C) 7 D) 9 https://www.youtube.com/watch?v=c5orJHRHbX0 (2013) __ NH4NO3 (s) __ N2 (g)+ __ O2 (g) + __ H2O (g) https://www.youtube.com/watch?v=TworcINhDhQSee 2:30 (1947)

  15. ANSWER Ammonium nitrate, when heated, decomposes into nitrogen gas, oxygen gas, and water vapor. What is the sum of the coefficients in the balanced equation using smallest integer coefficients? A) 3 B) 5 C) 7 D) 9 2 NH4NO3 (s) 2 N2 (g)+ 1 O2 (g) + 4 H2O (g)

  16. Chemical ReactionsBalancing Chemical Equations • Single Displacement • AB + C CB + A • Example: • HCl (aq) + Mg (s) MgCl2(aq) + H2(g) • Balanced Equation: ? 2 HCl (aq) + Mg (s) MgCl2(aq) + H2(g) Avogadro’s Law allows calculation of the Molar Mass of the gas from itsexperimental volume and calculated # of moles produced.

  17. Chemical ReactionsBalancing Chemical Equations • Double Displacement • AB + CD AD + CB • Example: • A solution of sodium phosphate reacts with a solution of silver nitrate to produce aqueous sodium nitrate and a precipitate of silver phosphate. • Balanced equation: ? Na3PO4(aq) + 3 AgNO3(aq) Ag3PO4(s) + 3 NaNO3(aq)

  18. Chemical ReactionsBalancing Chemical Equations • Combustion: • C8H18(l)+ O2(g) CO2(g) + H2O(l) • Oxygen reacts with octane to produce carbon dioxide and water. • The balanced equation: • 2 C8H18(l)+ 25 O2(g)16 CO2(g)+18 H2O(l) https://phet.colorado.edu/sims/html/balancing-chemical-equations/latest/balancing-chemical-equations_en.html

  19. QUESTION

  20. D) 13 O should be balanced last since it contains only one type of element and balancing it will not cause an imbalance in another element. ANSWER 2 C8H18 (l)+ 25 O2(g)16 CO2(g)+18 H2O(l) 2 C4H10(l)+ 13 O2(g)8 CO2(g)+ 10 H2O(l) 2

  21. QUESTION Consider the molecular view of reactants converted to a product in the boxes shown below: Which balanced equation best represents this reaction? A) NO + Cl2→ Cl2NO B) 2 NO + Cl2 → 2 ClNO C) N2 + O2 + Cl2 → 2 ClNO D) NO + Cl → ClNO

  22. ANSWER Consider the molecular view of reactants converted to a product in the boxes shown below: Which balanced equation best represents this reaction? A) NO + Cl2→ Cl2NO B) 2 NO + Cl2 → 2 ClNO C) N2 + O2 + Cl2 → 2 ClNO D) NO + Cl → ClNO

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