neutralization reactions

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 > 7

pH 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.