1 / 23

Writing Chemical Equations

Building Science Champions. Writing Chemical Equations. Objectives. Describe the information conveyed in a chemical equation. Apply the principle of conservation of mass to chemical reactions. Identify and describe three classes of chemical reactions. Key Terms. Chemical equation Subscript

Download Presentation

Writing Chemical Equations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Building Science Champions Writing Chemical Equations

  2. Objectives • Describe the information conveyed in a chemical equation. • Apply the principle of conservation of mass to chemical reactions. • Identify and describe three classes of chemical reactions.

  3. Key Terms • Chemical equation • Subscript • Reactant • Product • Conservation of mass • Coefficient • Synthesis • Decomposition • Replacement

  4. Chemical Equations • Chemical Equations are short, easy ways to show a chemical reaction by using elements’ symbols instead of words. • Symbols are easy to understand.

  5. Writing Chemical Equations • The formula will show the ratio of elements in a compound. • C12H22O11 is the chemical formula for sugar. • The letter corresponds to a particular element on the periodic table. • The subscript corresponds to the element that precedes the subscript. • If there is no subscript after a letter then there is one (1) of that particular element. • CO2

  6. Structure of an Equation • A chemical equation summarizes a chemical reaction. • The material you begin with is the REACTANT. • The completed reaction is the PRODUCT. Reactant + Reactant Product + Product = YIELDS

  7. Structure of an Equation • When there are two or more reactants they are separated by a plus sign. • When there are two or more products they are separated by a plus sign. • The ratio of products to reactant can change. Reactant + Reactant Product Reactant Product + Product Reactant + Reactant + Reactant Product

  8. Conservation of Mass • Regardless of the total number of reactants and products involved, all the atoms at the start of the reaction have to be present at the end of the reaction. • The amount of matter involved in a chemical reaction does not change. The total mass of the reactants must equal the total mass of the product.

  9. The LAW of CONSERVATION • The law of conservation states: • “Matter cannot be created nor destroyed during a chemical reaction.”

  10. Review • Chemical equations are short hand for chemical reactions. • Subscripts go to the element before them. • To the left of the yield signs are reactants and to the right are products. • There can be multiple products and reactants. • Matter cannot be created nor destroyed.

  11. Checkpoint • How do masses of the atoms in the reactants of a chemical reaction compare with the atoms in the products? • The number of atoms remain equal and the total of mass is unchanged.

  12. Balancing Chemical Equations • A chemical reaction must show the same number of each type of atom on both sides of the equation. • When this happens the equation is BALANCED.

  13. Balancing Equation • H2 + O2 H2O • Does the left side equal the right side? • 2 Hydrogen and 2 Oxygen on the left • 2 Hydrogen and 1 Oxygen on the right • Not equal. So what can be done to balance the equation?

  14. H2 + O2 H2O • Add a coefficient of 2 in front of the H2O • Coefficient is the number placed in front of chemical formulas in an equation. • A coefficient tells how many atoms or molecules there are. • The coefficient is factored out until the next sign. • H2+ O2 2 H2O • Left side – 2 Hydrogen and 2 Oxygen • Right side – 4 hydrogen and 2 Oxygen • How can we balance them out?

  15. H2 + O22 H2O • Place a 2 in front of the H2 in the reactant. • 2H2 + O2 2H2O • Left side – 4 Hydrogen and 2 Oxygen • Right side – 4 Hydrogen and 2 Oxygen • We are balanced!!!!!!!!!!!!!!!!!

  16. Mg + O2MgO • Left side – 1 Magnesium and 2 Oxygen • Right Side – 1 Magnesium and 1 Oxygen • Is the equation balanced? • Now what? • Add 2 in front of Magnesium in the reactant and Magnesium in the product. 2Mg + O2 2MgO • Are we balanced?

  17. You Try • C + Cl2 CCl4 • C + 2 Cl2 CCl4 • Al2O3 Al + O2 • 2 Al2O3 4 Al + 3 O2 • ***You can only change coefficients you CANNOT change subscripts. ***

  18. Classifying Chemical Reactions • There are 3 major classifications of chemical reactions: • Synthesis • Decomposition • Replacement

  19. Synthesis • When two or more substances combine to make a more complex substance the process is called synthesis. • Put things together. • Simple + Simple Complex • More reactants than products 2 SO2 + O2 + 2 H2O 2 H2SO4 Sulfur dioxide + Oxygen + water yields sulfuric acid

  20. Decomposition • Decomposition breaks down reactants into smaller products. • Complex Simple + Simple • More products than reactants 2 H2O2 2 H2O + O2 Hydrogen peroxide yields water and oxygen gas

  21. Replacement • When one element replaces another in a compound, or when 2 elements in different compound trade places, this is replacement. • Reactant + Reactant Product + Product CaCO3 + 2 HCl CaCl2 + H2O3 2 CuO + C 2 Cu + CO2

  22. Review • Chemical equations show chemical reactions • Matter cannot be created nor destroyed • Three types of chemical reactions • Synthesis • Decomposition • Replacement

  23. References • Anderson, M. et all (2012) Physical Science. McGraw-Hill: Columbus • Frank, D.V et al (2001). Physical Science. Prentice Hall: New Jersey

More Related