1 / 16

Introduction to Chemical Reactions and Equations

Introduction to Chemical Reactions and Equations. What are the clues that a chemical reaction has occurred?. A gas bubbles off. A new solid material is formed (a precipitate .). Color change. Heat and/or light are emitted. The key to chemical reactions!. The Law of Conservation of Mass

yasir-mcpherson
Télécharger la présentation

Introduction to Chemical Reactions and 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. Introduction to Chemical Reactions and Equations

  2. What are the clues that a chemical reaction has occurred?

  3. A gas bubbles off.

  4. A new solid material is formed (a precipitate.)

  5. Color change.

  6. Heat and/or light are emitted.

  7. The key to chemical reactions! The Law of Conservation of Mass In a chemical reaction, no atoms are created or destroyed. The atoms in the reacting molecules simply re-arrange to form new molecules. Since atoms aren’t created or destroyed, no mass is created or destroyed either. Mass is “conserved.”

  8. Count the atoms, before & after 2H2 + O2 2H2O

  9. In the reactionN2+ 3H22NH3 • If 14 grams of N2 reacted with 3 grams of H2, how many grams of ammonia would be produced? • If 58.5 grams of NaCl is decomposed, and 23 grams of Na is formed, how many grams of Cl2 must also be formed? In the reaction2NaCl 2Na + Cl2

  10. What else is conserved? • In N2 + 3H2 2NH3 besides mass (grams), what else is being conserved? • Atoms? • Molecules? • Moles?

  11. Coefficients • In a chemical reaction, if more than 1 molecule of a substance reacts or is produced, the number of molecules is shown with a coefficient. • 6CO2 + 6H2O C6H12O6 + 6O2 • Coefficients multiply subscripts through the whole molecule that follows, so 6CO2 shows that there are 6 Carbon atoms and 12 Oxygen atoms.

  12. How many? • How many of each atom are shown by 4Al2(SO4)3 • How many of each atom are shown by 3(NH4)3PO4

  13. Terminology • In a chemical reaction, the materials to the left of the arrow are the reactants. Reactants are consumed in the reaction. • The arrow is like an equal sign in math. It can be read “react to produce” or “produces” or “forms”. • The materials to the right of the arrow are the products. They form as the reaction proceeds. • H2O + SO3 H2SO4

  14. Phase Notation • A chemical equation can also show the physical state of the materials in the reaction. This is done with phase notations: • (s) solid (l) liquid (g) gas • (aq) aqueous or dissolved in water • (ppt) or ( ) means “a precipitate forms” • ( ) means “a gas bubbles off” • means “is heated” • Phase notations are written to the lower right of each formula. Clues to phase notations are often given in equations written in words.

  15. An example • When pellets of sodium hydroxide are dropped into an aqueous solution of iron(III) chloride, iron(III) hydroxide precipitates and sodium chloride stays dissolved. • 3NaOH(s) + FeCl3(aq) Fe(OH)3 (ppt) + 3NaCl(aq)

  16. Now onward to “balancing chemical equations”

More Related