Steps for balancing a chemical equation

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1 The Chemical Equation: A Chemical Recipe Dr. Gergens - SD Mesa College A. Learn the meaning of these arrows. B. The chemical equation is the shorthand notation for a chemical reaction. A chemical equation shows the molar quantities of reactants and products in a reaction. react to produce 1Reactants 1Products the number out in front of a substance in a balanced reaction is a molar quantity known as a molar coefficient B. Law of Conservation of Mass - Matter cannot be gained or lost in the process of a chemical reaction. The law of conservation of mass states that we must have a balanced equation. C. List five factors involved in the construction of an equation or "chemical recipe." 1. The identity of products and reactants must be specified. 2. Reactants are written to the left of the reaction arrow ( >) and products to the right. 3. The physical state of reactants and products is shown in parentheses; (s), (l), (g), and (aq) 4. The symbol over the reaction arrow mean that heat energy is necessary for the reaction to occur. 5. The equation must be balanced. Steps for balancing a chemical equation Step 1: Step 2: Step 3: Count the number of atoms of each element on both the product and reactant side. Determine which atoms are not balanced. Balance one atom at a time, using coefficients. Start with atoms that appear only once in the reactants and only once in the products. Usually leave Hydrogen atoms followed by Oxygen atoms until last. Step 4: After you believe that you have successfully balanced the equation, repeat Step 1, to be certain that mass conservation has been achieved. Note: DO NOT Change subscripts in a molecular formula (i.e., 2 NaCl X Na 2 Cl 2 ) 119

2 Double Displacement Reactions Demonstration Dr. Gergens - SD Mesa College Using the solubility rules for ionic salts (see your periodic table, front cover), predict whether mixing the two aqueous ionic salts (or aqueous strong acid) will produced an insoluble precipitate. CuSO4 (aq) NaNO3 (aq) HCl (aq) AgNO3 (aq) Na2CO3 (aq) CuSO4 (aq) all soluble all soluble Ag 2 SO 4 (s) CuCO 3 (s) NaNO3 (aq) all soluble all soluble all soluble HCl (aq) AgCl (s) H 2 O(l)+ CO 2 (g) AgNO3 (aq) Ag 2 CO 3 (s) Na2CO3 (aq) A. CuSO4 (aq) + NaNO3 (aq) No Reaction () B. CuSO4 (aq) + HCl (aq) C. 1 CuSO4 (aq) + 2 AgNO3 (aq) 1 Ag2 SO4 (s) + 1 Cu(NO3)2 (aq) D. CuSO4 (aq) + Na2CO3 (aq) E. NaNO3 (aq) + HCl (aq) F. 1 HCl (aq) + 1 AgNO3 (aq) 1 AgCl (s) + 1 NaNO 3 (aq) G. 2 HCl (aq) + 1 Na2CO3 (aq) 2 NaCl (aq) + 1 CO 2 (g) + 1 H 2 O(l) H. NaNO3 (aq) + AgNO3 (aq) I. NaNO3 (aq) + Na2CO3 (aq)

3 BALANCING PRACTICE Dr. Gergens - SD Mesa College a. Balance each of the following equations by adjusting the coefficients in front of the chemical formulas. b. List the physical state of each compound. c. Determine the driving force for each reaction. d. Classify each reaction in as many ways as possible. 1. Cu (s) + 2 AgNO 3 (aq) Cu(NO3 ) 2 (aq) + 2 Ag (s) Transfer of Electrons 2. 2 Al (s) + 3 S (s) Al2 S 3 (s) Transfer of Electrons 3. Na 2 CO 3 (aq) + CaCl 2 (aq) CaCO3 (s) + 2 NaCl (aq) Precipitation of CaCO Fe (s) + 3 Cl 2 (g) 2 FeCl3 (s) Transfer of Electrons 5. 2 Na 3 PO 4 (aq) + 3 BaCl 2 (aq) Ba3 (PO 4 ) 2 (s) + 6 NaCl (aq) Precipitation of Ba 3 (PO 4 ) NaOH (aq) + CuSO 4 (aq) Na2 SO 4 (aq) + Cu(OH) 2 (s) Precipitation of Cu(OH) 2 7. Mg(OH) 2 (s) + H 2 SO 4 (aq) MgSO4 (aq) + 2 H 2 O (l) Water Formation Acid-Base Reaction 8. 2 Al (s) + 6 HCl (aq) 2 AlCl3 (aq) + 3 H 2 (g) Hydrogen Gas Formation 9. 3 Mg (s) + 2 H 3 PO 4 (aq) Mg3 (PO 4 ) 2 (s) + 3 H 2 (g) Mg 3 (PO 4 ) 2 ppt & H 2 Gas 10. Br 2 (l) + 2 CuI (aq) 2 CuBr (aq) + I 2 (s) Transfer of Electrons reduced oxidized Single Replacement NaOH (aq) + FeCl 3 (aq) 3 NaCl (aq) + Fe(OH) 3 (s) Precipitation of Fe(OH) KBr (aq) + Pb(NO 3 ) 2 (aq) > 2 KNO3 (aq) + PbBr 2 (s) Precipitation of PbBr AlCl 3 (aq) + 3 H 2 SO 4 (aq) Al2 (SO 4 ) 3 (s) + 6 HCl (aq) Precipitation of Al 2 (SO 4 ) Al 2 (SO 4 ) 3 (aq) + 3 BaCl 2 (aq) 3 BaSO4 (s) + 2 AlCl 3 (aq) Precipitation of BaSO Cd(NO 3 ) 2 (aq) + H 2 S (l) CdS (s) + 2 HNO 3 (aq) Precipitation of CdS 116

4 DOUBLE REPLACEMENT REACTIONS AND PREDICTIONS PRACTICE Dr. Gergens - Mesa College a. Complete and balance each of the following equations for double replacement reactions. b. List the physical state of each compound. c. Determine the driving force for each reaction. 1. NaCl (aq) + AgNO 3 (aq) NaNO3 (aq) + AgCl (s) Precipitation of AgCl 2. BaCl 2 (aq) + H 2 SO 4 (aq) BaSO4 (s) + 2 HCl (aq) Precipitation of BaSO 4 3. NaOH (aq) + HCl (aq) NaCl (aq) + H 2 O (l) Water Formation 4. Na 2 CO 3 (aq) + 2 HCl (aq) 2 NaCl (aq) + H 2 O (l) + CO 2 (g) Water & Gas 5. H 2 SO 4 (aq) + 2 NaOH (aq) 2 H2 O (l) + Na 2 SO 4 (aq) Water Formation 6. FeCl 3 (aq) + 3 KOH (aq) Fe(OH)3 (s) + 3 KCl (aq) Precipitation of Fe(OH) 3 7. Na 2 SO 3 (aq) + 2 HCl (aq) 2 NaCl (aq) + H 2 SO 3 (l) Special Strong to Weak Acid 8. K 2 CrO 4 (aq) + Pb(NO 3 ) 2 (aq) 2 KNO3 (aq) + PbCrO 4 (s) Precipitation of PbCrO 4 9. NaC 2 H 3 O 2 (aq) + HNO 3 (aq) HC2 H 3 O 2 (l) + NaNO 3 (aq) Special Strong to Weak Acid 10. NaOH (aq) + NH 4 Cl (aq) NaCl (aq) + NH 3 (g) + H 2 O (l) Water & Gas BiCl 3 (aq) + 3 H 2 S (l) Bi2 S 3 (s) + 6 HCl (aq) Precipitation of Bi 2 S K 2 C 2 O 4 (aq) + 2 HCl (aq) 2 KCl (aq) + H 2 C 2 O 4 (l) Special Strong to Weak Acid H 3 PO 4 (aq) + 3 Ca(OH) 2 (aq) 6 H2 O (l) + Ca 3 (PO 4 ) 2 (s) Water & ppt of Ca 3 (PO 4 ) (NH 4 ) 2 CO 3 (aq) + 2 HBr (aq) 2 NH4 Br (aq) + H 2 O (l) + CO 2 (g) Water & Gas 15. (NH 4 ) 2 CO 3 (aq) + CaCl 2 (aq) 2 NH4 Cl (aq) + CaCO 3 (s) Precipitation of CaCO 3 117

5 MORE BALANCING PRACTICE Dr. Gergens - Mesa College a. Balance each of the following equations by adjusting the coefficients in front of the chemical formulas. b. List the physical state of each compound. c. Determine the driving force for each reaction. d. Classify each reaction in as many ways as possible Mg (s) + O 2 (g) 2 MgO (s) Transfer of Electrons 2. 2 KClO 3 (s) 2 KCl (s) + 3 O 2 (g) Transfer of Electrons reduced Decomposition oxidized 3. 3 Fe (s) + 2 O 2 (g) Fe3 O 4 (s) Transfer of Electrons 4. Mg (s) + 2 HCl (aq) MgCl2 (aq) + H 2 (g) Transfer of Electrons 5. 2 Na (s) + 2 H 2 O (l) 2 NaOH (aq) + H 2 (g) Transfer of Electrons 6. 3 Fe (s) + 4 H 2 O (l) Fe3 O 4 (s) + 4 H 2 (g) Transfer of Electrons Beneath each word equation write the formula equation and balance it S (s) + O 2 (g) SO2 (g) Transfer of Electrons 8. Zn (s) + H 2 SO 4 (aq) ZnSO4 (aq) + H 2 (g) Transfer of Electrons 9. C (s) + O 2 (g) CO2 (g) Transfer of Electrons H 2 (g) + O 2 (g) 2 H2 O (l) Transfer of Electrons Al (s) + 6 HCl (aq) 2 AlCl3 (aq) + 3 H 2 (g) Transfer of Electrons K (s) + 2 H 2 O (l) 2 KOH (aq) + H 2 (g) Transfer of Electrons 13. NaHCO 3 (s) + HC 2 H 3 O 2 (aq) > NaC2 H 3 O 2 (aq) + H 2 O (l) + CO 2 (g) You can try this chemical reaction at home! NO transfer of electrons 118

6 2. 2 AgNO 3 (aq) + CaBr 2 (aq) > 2 AgBr (s) + Ca(NO 3 ) 2 (aq) a. 2 Ag + (aq) + 2 NO Ca 2+ (aq) + 2 Br > 2 AgBr (s) + Ca 2+ (aq) + NO 3 b. Ag + (aq) + Br > AgBr (s) 3. NaCN (aq) + HCl (aq) > NaCl (aq) + HCN (g,aq) a. Na + (aq) + CN + H + (aq) + Cl > Na + (aq) + Cl + HCN (g,aq) b. H + (aq) + CN > HCN (g,aq) 4. AgCN (aq) + HCl (aq) > AgCl (s) + HCN (g,aq) a. Ag + (aq) + CN + H + (aq) + Cl > AgCl (s) + HCN (g,aq) b. Ag + (aq) + CN + H + (aq) + Cl > AgCl (s) + HCN (g,aq) 5. Ba(OH) 2 (aq) + Na 2 SO 4 (aq) > BaSO 4 (s) + 2 NaOH (aq) a. Ba 2+ (aq) + 2 OH + 2 Na + (aq) + SO > BaSO 4 (s) + 2 Na + (aq) + 2 OH b. Ba 2+ (aq) + SO > BaSO 4 (s) 6. Na 2 S (aq) + Hg(NO 3 ) 2 (aq) > 2 NaNO 3 (aq) + HgS (s) a. 2 Na + (aq) + S 2 + Hg 2+ (aq) + 2 NO > 2 Na + (aq) + 2 NO 3 + HgS (s) b. Hg 2+ (aq) + S > HgS (s) 7. ZnCl 2 (aq) + H 2 S (aq, g) > ZnS (s) + 2 HCl (aq) a. Zn 2+ (aq) + 2 Cl + 2 H + (aq) + S > ZnS (s) + 2 H + (aq) + 2 Cl b. Zn 2+ (aq) + S > ZnS (s) 8. Na 2 S (aq) + 2 HCl (aq) > 2 NaCl (aq) + H 2 S (aq, g) a. 2 Na + (aq) + S H + (aq) + 2 Cl > 2 Na + (aq) + 2 Cl + H 2 S (aq, g) b. 2 H + (aq) + S > H 2 S (aq, g) 9. 2 KC 2 H 3 O 2 (aq) + H 2 SO 4 (aq) > K 2 SO 4 (aq) + 2 HC 2 H 3 O 2 (l) a. 2 K + (aq) + 2 C 2 H 3 O H + (aq) + SO > 2 K + (aq) + SO HC 2 H 3 O 2 (l) b. H + (aq) + C 2 H 3 O > HC 2 H 3 O 2 (l)

7 10. HC 2 H 3 O 2 (l) + KOH (aq) > H 2 O (l) + KC 2 H 3 O 2 (aq) a. HC 2 H 3 O 2 (l) + K + (aq) + OH > H 2 O (l) + K + (aq) + C 2 H 3 O 2 b. C 2 H 3 O 2 (l) + OH > H 2 O (l) + C 2 H 3 O NH 4 OH (aq) + HCl (aq) > NH 4 Cl (aq) + H 2 O (l) a. NH 4 + (aq) + OH + H + (aq) + Cl > NH 4 + (aq) + Cl + H 2 O (l) b. H + (aq) + OH > H 2 O (l) NH 4 OH (aq) + FeCl 3 (aq) > 3 NH 4 Cl (aq) + Fe(OH) 3 (s) a. 3 NH 4 + (aq) + 3 OH + Fe 3+ (aq) + 3 Cl > 3 NH 4 + (aq) + 3 Cl + Fe(OH) 3 (s) b. Fe 3+ (aq) + 3 OH > Fe(OH) 3 (s) HNO 3 (aq) + Ca(OH) 2 (aq) > 2 H 2 O (l) + Ca(NO 3 ) 2 (aq) a. 2 H + (aq) + 2 NO 3 + Ca 2+ (aq) + 2 OH > 2 H 2 O (l) + Ca 2+ (aq) + 2 NO 3 b. H + (aq) + OH > H 2 O (l) AgNO 3 (aq) + Na 2 S (aq) > Ag 2 S (s) + 2 NaNO 3 (aq) a. 2 Ag + (aq) + 2 NO Na + (aq) + S > Ag 2 S (s) + 2 Na + (aq) + 2 NO 3 b. Ag + (aq) + S > Ag 2 S (s) 15. Cu(CN) 2 (aq) + 2 HCl (aq) > CuCl 2 (aq) + 2 HCN (g,aq) a. Cu 2+ (aq) + 2 CN + 2 H + (aq) + 2 Cl > Cu 2+ (aq) + 2 Cl + 2 HCN (g,aq) b. H + (aq) + CN > HCN (g,aq) Pb(NO 3 ) 2 (aq) + 2 AlCl 3 (aq) > 3 PbCl 2 (s) + 2 Al(NO 3 ) 3 (aq) a. 3 Pb 2+ (aq) + 6 NO Al 3+ (aq) + 6 Cl > 3 PbCl 2 (s) + 2 Al 3+ (aq) + 6 NO 3 b. Pb 2+ (aq) + 2 Cl > PbCl 2 (s) AgC 2 H 3 O 2 (aq) + MgSO 4 (aq) > Ag 2 SO 4 (s) + Mg(C 2 H 3 O 2 ) 2 (aq) a. 2 Ag + (aq) + 2 C 2 H 3 O 2 + Mg 2+ (aq) + SO > Ag 2 SO 4 (s) + Mg 2+ (aq) + 2 C 2 H 3 O 2 b. 2 Ag + (aq) + SO > Ag 2 SO 4 (s)

8 18. HC 2 H 3 O 2 (l) + NH 4 OH (aq) > H 2 O (l) + NH 4 C 2 H 3 O 2 (aq) a. HC 2 H 3 O 2 (l) + NH 4 + (aq) + OH > H 2 O (l) + NH 4 + (aq) + C 2 H 3 O 2 b. HC 2 H 3 O 2 (l) + OH > H 2 O (l) + C 2 H 3 O Fe(NO 3 ) 3 (aq) + K 3 PO 4 (aq) > FePO 4 (s) + 3 KNO 3 (aq) a. Fe 3+ (aq) + 3 NO K + (aq) + PO > FePO 4 (s) + 3 K + (aq) + 3 NO 3 b. Fe 3+ (aq) + PO > FePO 4 (s) 20. Na 2 CO 3 (aq) + H 2 SO 4 (aq) > Na 2 SO 4 (aq) + H 2 O (l) + CO 2 (g) a. 2 Na + (aq) + CO H + (aq) + SO > 2 Na + (aq) + SO H 2 O (l) + CO 2 (g) b. 2 H + (aq) + CO > H 2 O (l) + CO 2 (g) 21. Cu(NO 3 ) 2 (aq) + 2 NaOH (aq) > Cu(OH) 2 (s) + 2 NaNO 3 (aq) a. Cu 2+ (aq) + 2 NO Na + (aq) + 2 OH > Cu(OH) 2 (s) + 2 Na + (aq) + 2 NO 3 b. Cu 2+ (aq) + 2 OH > Cu(OH) 2 (s) Explain why each of the following mixing of reactants affords no reaction,. 22. NaNO 3 (aq) + HCl (aq) > Both products are soluble 23. Pb(NO 3 ) 2 (aq) + Hg(NO 3 ) 2 (aq) > Both products are reactants 24. CsCl (aq) + (NH 4 ) 2 SO 4 (aq) > Both products are soluble 25. K 2 SO 4 (aq) + NaClO 4 (aq) > Both products are soluble