1 / 15

Chemical Reactions How do you know if a chemical reactions takes place? A color change takes place

Chemical Reactions How do you know if a chemical reactions takes place? A color change takes place A solid (ppt) forms Bubbles are formed without heating A flame occurs Light or heat is given off/absorbed Water is produced. Chemical Equations. H 2 SO 4 + 2 NaOH  Na 2 SO 4 + 2 H 2 O

rusty
Download Presentation

Chemical Reactions How do you know if a chemical reactions takes place? A color change takes place

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. Chemical Reactions How do you know if a chemical reactions takes place? • A color change takes place • A solid (ppt) forms • Bubbles are formed without heating • A flame occurs • Light or heat is given off/absorbed • Water is produced

  2. Chemical Equations H2SO4 + 2 NaOH  Na2SO4 + 2 H2O • Reactants on the left, products on the right • “” indicates a chemical reaction • “+” separates the substances • “2” coefficient - how many of that substance (big number out front) • “4” subscript – how many of the preceding atom (little numbers)

  3. Law of Conservation of Mass Mass can not be created or destroyed in a chemical reaction. It can only change form. This means in a chemical reaction, there must be the same number of each type of atom on both sides of the arrow.

  4. Balancing Equations • Copy formulas correctly • Subscripts can not be changed • Change only the coefficients • Determine the most complicated compound. Calculate the number of each atom/ion in that compound • Go to other side of reaction, use coefficients to get the same number of ions • Repeat until all ions are balanced.

  5. Sometimes it is easier to balance equations when water is written as HOH, sometimes it is easier when it is written as H2O. The coefficient of “1” is not written, it is understood. __ HCl + __ Ca(OH)2 __ CaCl2 + __ H2O This is easier to balance if written as __ HCl + __ Ca(OH)2 __ CaCl2 + __ HOH 2 HCl + Ca(OH)2  CaCl2 + 2 HOH

  6. Balance the following reactions: __Ba(NO3)2 + __NaCl  __BaCl2 + __NaNO3 __ Al + __ O2 __Al2O3 __ C7H16 + __ O2 __ CO2 + __ H2O • Ba(NO3)2 + 2 NaCl  BaCl2 + 2 NaNO3 • 4 Al + 3 O2  2 Al2O3 • C7H16 + 11 O2 7 CO2 + 8 H2O

  7. The 5 types of equations • Combination (or Synthesis) – A + B  AB. This forms a new compound from two or more reactants. 2 H2 + O2 2 H2O 2. Decomposition – AB  A + B. A single reactant breaks up into two or more products. This is the opposite of a combination reaction. 2 HgO  2 Hg + O

  8. Single Replacement A + BX  AX + B or A + BX  BA + X A single element replaces an element in a compound. A metal replaces the metal, a nonmetal replaces the nonmetal in the compound. Cl2 + 2 NaBr  2 NaCl + Br2 Cs + NaCl  CsCl + Na

  9. 4. Double Replacement – AB + CD  AD + CB The positive ions in two different compounds are swapping places, or the negative ions in two different compounds are swapping places. H3PO4 + 3 NaOH  Na3PO4 + 3 HOH

  10. 5. Combustion – CxHy (CxHyOz) + O2 CO2 + H2O “Burning” or the rapid oxidation of a carbon compound into carbon dioxide and water. CH4 + 2 O2  CO2 + 2 H2O 2 CH3OH + 3 O2  2 CO2 + 4 H2O

  11. Tips for recognizing and balancing reactions: Combination : 2 reactants  1 product Decomposition : 1 reactant  2 products Single : element + cmpd  element + cmpd Double : elements in 2 cmpds are exchanged Combustion : CH(O) + O2  CO2 + H2O

  12. If your first guess of coefficients doesn’t work, change your guess and start over. • Coefficient x subscript = # of atoms/ions • Be consistent – balance the reactions the same way each time. • Be right – Know when to add numbers together, and when to multiply numbers together.

  13. Predicting the products of reactions • Identify the type of reaction: combination, combustion or double replacement. • Complete the reaction with the correct formulas based on the type of reaction. • Balance the reaction once all of the complete formulas have been written.

  14. To complete the reaction with correct formulas: • Combination: the compound formed will be the one formed from the elements as “ions” • Combustion: the products will always be CO2 and H2O • Double replacement: switch the positive ions, get the correct formulas by “cross method”. Subscripts in the original compound don’t matter unless they are part of the actual ion (a polyatomic ion).

  15. Changing from word problems to equations • HOFBrINCl or Lucky 7 • Solid (s), liquid (l), gas (g), aqueous (aq) • Write all of the correct formulas, reactants on the left and products on the right. • Balance the reaction

More Related