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General Reactions

General Reactions. Dr. Ron Rusay. 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)

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General Reactions

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  1. General Reactions Dr. Ron Rusay

  2. 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

  3. The Reaction of Sodium & Chlorine

  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. General Chemical Reactions

  7. Chemical Reactions • Combination (Synthesis) • A + B -----> C • Example: • H2 (g) + O2 (g) -----> H2O (g) • Balancing (Conservation of Atoms): • 2 H2 (g) + O2 (g) -----> 2 H2O (g)

  8. Synthesis of Water

  9. An Unwanted Synthesis of WaterCombustion & the Hindenburg 1937

  10. Chemical Reactions • Decomposition • A ----> B + C • 2 NI3 (s) ---> N2 (g) + 3 I2 (s)

  11. Decomposition • Another example: • Potassium chlorate (s) + heat -----> potassium chloride (s) + oxygen (g) • Balanced equation: ?

  12. QUESTION 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

  13. 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

  14. Chemical Reactions • Single Displacement • AB + C ----> CB + A • Example: • HCl (aq) + Mg (s) ----> MgCl2(aq) + H2(g) • Balanced Equation: ?

  15. Single Displacement(Oxidation / Reduction) • Write a balanced equation for the following reaction:

  16. Chemical Reactions • 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: ?

  17. Chemical Equations • Combustion: • C8H18(l)+ O2(g) -----> CO2(g) + H2O(l) • Oxygen reacts with octane to produce carbon dioxide and water. • Reminder: the equation must balance: • 2 C8H18(l)+ 25 O2(g)-----> 16 CO2(g)+18 H2O(l)16 CO2(g)+18 H2O(l)

  18. QUESTION

  19. 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

  20. 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

  21. 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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