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Writing Equations 1.Word Equation 2.Skeleton Equation 3.Balanced Equation –Formulas –Show all the ions –Net Ionic Equation
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Neutralization ReactionsNeutralization Reactions
• AcidAcid + BaseBase Salt + Water• Double Replacement• HX(aq)HX(aq) + MOH(aq)MOH(aq) MX(aq) + H2O(l)• Not Redox• Balance by counting atoms
Writing Equations
1. Word Equation2. Skeleton Equation3. Balanced Equation
– Formulas– Show all the ions– Net Ionic Equation
Formulas for Salts• Positive ion 1st. Negative ion 2nd.• Write down symbols & charges.• If charges don’t cancel, use criss-cross rule.
HNOHNO33 + KOH + KOH H H22O + saltO + salt
• K+1 + NO3-1 KNO3
HH22SOSO44 + KOH + KOH H H22O + saltO + salt
• K+1 + (SO4)-2 K2SO4
Hydrochloric Acid + Sodium Hydroxide
HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
Sodium Chloride + Water
HCl(aq) + NaOH(aq) NaCl(aq) + H2Oor
H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)
H2O(l) + Na+ + Cl-(aq)
NaNa++ and Cl and Cl-- are spectator ions: are spectator ions:
H+(aq) + OH-(aq) H2O(l)
Nitric Acid + Potassium Hydroxide
HNOHNO33(aq) + KOH(aq) (aq) + KOH(aq) KNO KNO33(aq) + H(aq) + H22O(l)O(l)
HH++(aq) + NO(aq) + NO33--(aq) + K(aq) + K++(aq) + OH(aq) + OH--(aq) (aq)
KK++(aq) + NO(aq) + NO33--(aq) + H(aq) + H22O(l)O(l)
HH++(aq) + OH(aq) + OH--(aq) (aq) H H22OO
Sulfuric Acid + Calcium Hydroxide
HH22SOSO44(aq) + Ca(OH)(aq) + Ca(OH)22(aq) (aq)
CaSOCaSO44(aq) + H(aq) + H22O(l)O(l)
HH22SOSO44 + Ca(OH) + Ca(OH)22
CaSOCaSO44 + + 22 H H22OO
H2SO4(aq) + KOH(aq) ?
KK22SOSO44(aq) + H(aq) + H22O(l)O(l)
HH22SOSO44 + + 22 KOH KOH K K22SOSO44 + + 22 H H22OO
What is the ionic equation?What is the ionic equation?
2H2H++(aq) + SO(aq) + SO44-2-2(aq) + 2K(aq) + 2K++ (aq) + 2OH (aq) + 2OH-- (aq) (aq)
2K2K++(aq) + SO(aq) + SO44-2-2(aq) + 2H(aq) + 2H22O(l)O(l)
What is the net ionic equation?
2H2H++(aq) + 2OH(aq) + 2OH--(aq) (aq) 2H 2H22O(l)O(l)
Divide through by 2:Divide through by 2:
HH++(aq) + OH(aq) + OH--(aq) (aq) H H22O(l)O(l)
Hydrochloric Acid + Magnesium Hydroxide
HCl + Mg(OH)HCl + Mg(OH)22 MgCl MgCl22 + H + H22OO
HCl + Mg(OH)HCl + Mg(OH)22 MgCl MgCl22 + H + H22OO
2HCl + Mg(OH)2HCl + Mg(OH)22 MgCl MgCl22 + 2H + 2H22OO
What is the ionic equation?What is the ionic equation?
HH++(aq) + OH(aq) + OH--(aq) (aq) H H22O(l)O(l)
2H2H++(aq) + 2Cl(aq) + 2Cl--(aq) + Mg(aq) + Mg+2+2(aq) + 2OH(aq) + 2OH--(aq) (aq)
MgMg+2+2(aq) + 2Cl(aq) + 2Cl-1-1(aq) + 2H(aq) + 2H22O(l)O(l)
What is the net ionic equation?What is the net ionic equation?
2H2H++ + 2OH + 2OH-- 2H 2H22OO
For any neutralization reaction
• The net ionic equation is always:
H+ + OH- H2O
pH changes during neutralization
• Start with an acid.• Add a base• At neutralization
• Start with a base.• Add an acid.• At neutralization
pH < 7pH < 7pH pH
pH = 7pH = 7
pH > 7pH > 7pH pH
pH = 7pH = 7
HH++(aq) + OH(aq) + OH--(aq) (aq) H H22O(l)O(l)
1-to-1 relationship between H1-to-1 relationship between H++ and OH and OH--..
At neutralization, # of moles H# of moles H++ = # of moles OH = # of moles OH--
Molarity of H+
Molarity of HMolarity of H++ = = moles Hmoles H++
liters of solnliters of soln
Moles HMoles H++ = Molarity of H = Molarity of H++ X Liters soln X Liters soln
Moles HMoles H++ = M = MH+H+ X V X VH+H+
Molarity of OH-
Molarity of OHMolarity of OH-- = = moles OHmoles OH--
liters of solnliters of soln
Moles OHMoles OH-- = Molarity of OH = Molarity of OH-- X Liters soln X Liters soln
Moles OHMoles OH-- = M = MOH-OH- X V X VOH-OH-
At neutralization
Moles HMoles H++ = Moles OH = Moles OH--
MMH+H+ X V X VH+H+ = M = MOH-OH- X V X VOH-OH-
Titration Problems
• Rely on the fact that for all neutralization reactions, there must be a one-to-oneone-to-one ratio of H+ to OH-.
MA X VA = MB X VB
• MA = molarity of H+
• VA = volume of acid (mls, usually)
• MB = molarity of OH-
• VB = volume of base (mls, usually)Holds for monoprotic acid with monohydroxy Holds for monoprotic acid with monohydroxy base, diprotic acid with dihydroxy base, etc.base, diprotic acid with dihydroxy base, etc.
Modify MaVa = MbVb
• If the number of H’s in the acid does NOT equal the number of OH’s in the base, this equation MUST be modified:
naMaVa = nbMbVb
• Where na = subscript of H in formula for acid and nb = subscript of OH in formula for base.
Molarity of HMolarity of H++
• In HCl: molarity H+ = molarity HCl
• In H22SO4:
molarity H+ = 22(molarity H2SO4)• In H33PO4:
molarity H+ = 33(molarity H3PO4)
Molarity of OHMolarity of OH--
• In KOH:molarity OH- = molarity KOH
• In Ca(OH)22:
molarity OH- = 22(molarity Ca(OH)2)• Etc.
Titration Movie
On the buret, the numbers go down, On the buret, the numbers go down, so you read down.so you read down.
Notice that the volume units will Notice that the volume units will cancel out. They have to be the cancel out. They have to be the same, but not necessarily liters.same, but not necessarily liters.
