1 / 13

Chemistry Lecture Notes Writing and Balancing Chemical Equations

Chemistry Lecture Notes Writing and Balancing Chemical Equations. other info. Chemical Equations. coefficients. 3H 2 ( g ) + N 2 ( g )  2NH 3 ( g ) balanced (Dalton). reactants. products. general: A( l ) + B( s ) C( g ) + D( aq ) + heat ( s ) = solid heat produced: exothermic

genna
Télécharger la présentation

Chemistry Lecture Notes Writing and Balancing 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. Chemistry Lecture Notes Writing and Balancing Chemical Equations

  2. other info Chemical Equations coefficients 3H2(g) + N2(g)  2NH3(g)balanced (Dalton) reactants products general: A(l) + B(s) C(g) + D(aq) + heat (s) = solid heat produced: exothermic (l) = liquid heat consumed: endothermic (g) = gas (aq) = aqueous other info: temperature, pressure, catalyst, etc.

  3. Balancing Chemical Equations • Balancing chemical equations is generally done “by inspection,” but here are some common steps: • Write the unbalanced equation (often it is written for you). • Start by balancing the most complex substance (often but not always). • Choose an element that appears in only one reactant and product (always). • Balance by adjusting the coefficients so that there are the same number of atoms of each element on both sides. • Balance polyatomic ions (if present) as a unit. • Balance the remaining atoms, usually ending with the least complex substance, using fractional coefficients if necessary. • If fractional coefficients have been used, multiply both sides of the equation by the denominator to obtain whole numbers. • Do not alter any formulas (change subscripts). • Do not add or delete any reactants or products. • Use the smallest set of whole numbers. • Double check to be sure there are the same number of atoms of each kind on both sides of the equation.

  4. Balancing Chemical Equations P4O10(s) + H2O(l)  H3PO4(aq) Cu(s) + AgNO3(aq)  Cu(NO3)2(aq) + Ag(s) Ca(s) + NH3(g)  CaH2(s) + Ca3N2(s) K(s) + H2O(l)  KOH(aq) + H2(g) The combustion of butane (C4H10)

  5. Balancing Chemical Equations • Common polyatomic ions

  6. Double Displacement Reactions • Double displacement (metathesis) reactions: reactions in which anions and cations exchange partners • general: A+B(aq) + C+D(aq)  A+D(aq) + CB(?) • if: CB(s) precipitate • CB(aq) weak electrolyte or nonelectrolyte • CB(g) gas • C+B(aq) ionic (soluble) no net reaction net reaction has occurred

  7. Double Displacement Reactions • Precipitate-forming reactions • Solubility Rules: • Soluble compounds • all salts of alkali metal ions and the NH4+ ion • all salts of NO3, C2H3O2, ClO4 ions • most salts of Cl, Br, and I ions • except Ag+, Pb+2, and Hg2+2 salts • most salts of the SO42 ion • except Sr+2, Ba+2, Pb+2, and Hg2+2 salts • (CaSO4 is slightly soluble) • Insoluble compounds • most salts of CO32, PO43, OH, O2, and S2 ions • except alkali metal and NH4+ salts • (hydroxides and sulfides of Ca2+, Sr2+, and Ba2+ are slightly to moderately soluble)

  8. Double Displacement Reactions • Precipitate-forming reactions Complete and balance the following reactions in aqueous solution, indicating the state of each reactant and product: AgNO3 + NaBr CuCl2 + KOH Ba(NO3)2 + Na2SO4 Zn(C2H3O2)2 + Na2S

  9. Double Displacement Reactions • Acids and bases Arrhenius: acid - produces H3O+(aq) in water (formula starts with an H) base - produces OH(aq) in water (OH– salts or amines) HCl(aq) H3O+(aq) + Cl(aq) 100% dissociated strong acid HC2H3O2(aq) H3O+(aq) + C2H3O2(aq) 0.4% dissociated weak acid NaOH(aq) Na+(aq) + OH(aq) 100% strong base NH3(aq) NH4+(aq) + OH(aq) 0.4% weak base

  10. Double Displacement Reactions • Acid-base neutralization reactions HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) acid base salt water (nonelectrolyte) Complete and balance the following reactions: HClO4(aq) + KOH(aq)  HNO3(aq) + Ca(OH)2(aq) 

  11. Double Displacement Reactions • Gas-forming reactions • Reactions that produce gases: H2S, NH3, CO2 • K2S(aq) + 2HNO3(aq)  H2S(g) + 2KNO3(aq) • NH4Cl(aq) + KOH(aq)  NH4OH(aq) + KCl(aq) • but: NH4OH(aq)  NH3(g) + H2O(l) •  NH4Cl(aq) + KOH(aq)  NH3(g) + H2O(l) + KCl(aq) • Na2CO3(aq) + 2HCl(aq)  H2CO3(aq) + 2NaCl(aq) • but: H2CO3(aq)  CO2(g) + H2O(l) •  Na2CO3(aq) + 2HCl(aq)  CO2(g) + H2O(l) + 2NaCl(aq) correct equation correct equation

  12. Double Displacement Reactions • Gas-forming reactions Complete and balance the following reactions. CuS(s) + HCl(aq)  HCl(aq) + BaCO3(s)  NaOH(aq) + NH4NO3(aq) 

More Related