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Reactions in Chemistry

Reactions in Chemistry. Writing Balanced Chemical Equations. Writing reaction equations. Before you can write a balanced chemical equation for a reaction, you need to write an unbalanced equation. To do this you need to identify several things: What chemicals are reacting?

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Reactions in Chemistry

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  1. Reactions in Chemistry Writing Balanced Chemical Equations

  2. Writing reaction equations • Before you can write a balanced chemical equation for a reaction, you need to write an unbalanced equation. To do this you need to identify several things: • What chemicals are reacting? • What is the proper formula for each chemical? • What type of reaction is it? • What are the products that will be produced? • What are their proper formulas?

  3. Types of chemical reactions • Remember, the five basic categories of reactions are: • Synthesis (a.k.a. Direct Combination) • Decomposition

  4. Types of chemical reactions • Single Replacement • Double Replacement

  5. Types of chemical reactions • Combustion • An element or compound reacts with oxygen, often producing energy in the form of heat and light. • If a hydrocarbon undergoes combustion, the products are normally CO2 and water.

  6. Things to remember • When writing the chemical formulas: • Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine are diatomic molecules. • When deciding on formulas for binary ionic compounds, use the crisscross method and remember to reduce the ratio of atoms if possible. • Be sure that all chemical formulas are correct and that all reactants and products have been included before trying to balance the equation.

  7. Example 1 • A strip of magnesium is placed in a hydrochloric acid solution, and hydrogen gas is released. Write a balanced equation for the reaction that takes place. What are the reactants? What are their formulas? • Magnesium metal and hydrochloric acid. • Mg and HCl

  8. Example 1 (cont) What type of reaction would this be? What are the products? (Were all of them mentioned?) What are their formulas? • Single replacement • Magnesium chloride and hydrogen gas. • MgCl2 and H2

  9. Example 1 (cont) What would the unbalanced equation be? Now balance it: ReactantsProducts Mg – Mg – H – H – Cl – Cl –

  10. Example 2 • Potassium chlorate decomposes, to evolve oxygen. What are the reactants? What are their formulas? • Only potassium chlorate • KClO3

  11. Example 2 (cont) What type of reaction would this be? What are the products? (Were all of them mentioned?) What are their formulas? • Decomposition • Oxygen and potassium chloride • O2 and KCl

  12. Example 2 (cont) What would the unbalanced equation be? Now balance it: ReactantsProducts K – K – Cl – Cl – O – O –

  13. Example 3 • Copper(II) sulfate reacts with a sodium hydroxide solution. What are the reactants? What are their formulas? • Copper(II) sulfate and sodium hydroxide. • CuSO4 and NaOH

  14. Example 3 (cont) What type of reaction would this be? What would the products be? What are their formulas? • Double replacement • Copper(II) hydroxide and sodium sulfate • Cu(OH)2 and Na2SO4

  15. Example 3 (cont) What would the unbalanced equation be? Now balance it: ReactantsProducts Cu – Cu – SO4 – SO4 – Na – Na – OH – OH –

  16. Example 4 • The reaction that takes place in a butane lighter. (butane is C4H10) What type of a reaction is this? What would the reactants be? • Burning would indicate combustion • Butane and oxygen

  17. Example 4 (cont) What are the formulas for the reactants? What would the products be? What are their formulas? • C4H10 and O2 • Combustion results in carbon dioxide and water • CO2 and H2O

  18. Example 4 (cont) What would the unbalanced equation be? Now balance it: ReactantsProducts C – C – H – H – O – O –

  19. Example 5 • Soda pop gets its acidic taste because as carbon dioxide is forced to dissolve in the pop, it combines with water forming an acid. What type of a reaction is this? What would the reactants be? • Synthesis (or direct combination) • Carbon dioxide and water

  20. Example 5 (cont) What are the formulas for the reactants? What would the products be? What are their formulas? • CO2 and H2O • Synthesis results in only one product. • In this case it would be carbonic acid. • Only H2CO3

  21. Example 5 (cont) What would the unbalanced equation be? Now balance it: ReactantsProducts C – C – O – O – H – H –

  22. Resources: • http://wps.prenhall.com/wps/media/objects/165/169519/GIFS/AAAUAUH0.JPG • http://reich-chemistry.wikispaces.com/file/view/hcl3.gif/32672567/hcl3.gif • http://www.eatlikenoone.com/wp-content/uploads/2010/01/CocoFizz.JPG

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