Agenda 5-13-07Do Now:

1.write the products of the reaction when the reactants given below undergoes double replacement reaction and balanced the equation: AB + CD -----> CB + AD

HCl(aq) + Mg(OH)2(s) ------> 2. Define the ff on page 525 - 528: buffer solution, standard

solution, titration and equivalence point

HW for tomorrow: Check website under HW

Objectives Explain Neutralization Reaction in terms of acid base reaction Solve problems involving neutralization in acid base reaction To understand the general characteristic of buffered solution

Upcoming: Test on Friday ( types of decays, nuclear stability, half-life, acid-base reaction) Don’t Forget to study!

What is the difference between Acid And base according to Arrhenius Theory?

What’s the difference?

Acid produces H+ in aqueous solution

HCl (g) ------------> H +(aq) Cl- (aq)

Bases Produces OH- in aqueous Solution

NaOH (s) -----> Na+(aq) + OH-(aq)

What is the difference between Acid And base according to Bronsted-Lowry Theory?

What’s the difference?

What is an indicator?

Indicator

Substances that exhibit different colors in acidic and basic solutions

It has a weak acid and a conjugate base

Explain neutralization reaction

Objective #1

What happen when an acid reacts with a base?HCl + NaOH ---> HCl + NaOH ---> H2O + NaCl

Neutralization Reaction a type of double replacement reaction A reaction between an acid and a base to form a

neutral solution

Neutralization Reaction

Acid and base properties combine to form water

H+ + OH- -------> H2O

Note: water is one of the products of neutralization reaction

Exercise

Write the products of the reaction below and balance the equation

H2SO4 + NH4OH ---->

H2SO4 + NH4OH ----> (NH4)2SO4 + H2O

H2SO4 + 2 NH4OH ----> (NH4)2SO4 + 2 H2O

Acid Base TitrationIs a useful application of neutralization reactionA process of adding a solution of accurately known concentration, standard solution, ( titrant) to another solution of unknown concentration,( analyte until the chemical reaction between the two is complete ( the equivalence point) or end point

Equivalence point is the point in titration where the indicator used undergoes a color change

Note; indicator changes color at pH=7

How Does it Work?Load the titrant to OH- Base the burette and add the OH-titrant slowly to the analyte OH-OH- until exactly enough base OH-has been added to just react withall the analyte

Acid with indicator

H+ H+

H+ H+-

OH- OH-OH-

OH-

Has reached its equivalence point

H+ H+

At the equivalence point, n Acid = n base, to get the molarity of the base or acid M = n = moles V L

M acid = n acid , M base = n bas

V acid Vbase

nA = nB

MAVA = MBVB

Ex:In a titration, It takes 6mL of 0.5MNaOH to neutralize 15mL of HCl. What is the concentration of HCl?

NaOH + HCl -----> NaCl + H2O

molar ratio ( 1:1) MA VA = MBVB

MA = MBVB = (0.500M)(6mL)

VA 15mL

= 0.2M

Sample 2A 25.0mL of sulfuric acid solution requires 32.58mL of .500M NaOH to neutralize it. What is the molarity of H2SO4?

Solution:1.Write the balance equation H2SO4 + NaOH --->

H2SO4 + NaOH ---> Na2SO4 + H2O

H2SO4 + 2 NaOH ---> Na2SO4 + 2 H2O

2mole NaOH : 1 mole H2SO4

2.Determine the number of moles of NaOH M = n , n = MV n = (0.500moles) ( 0.03258L) = 0.01629 moles V L3.Determine the molarity of H2SO4 using nA = nB

M = n , M = 0.01629moles NaOH x 1mole H2SO4

V 0.025L 2mole NaOH M H2SO4 = 0.3258M

Prob.#1What volume of 1.5M NaOH is needed to react with 25mL of 4M HCl?

Solution: 1.Write the balanced equation: HCl + NaOH ----> NaCl + H2O

Ans VB = 67mL or 0.067L

Problem#2In a titration, 50.0mL 0f 0.1204 M HCl requires

48.54mL NaOH solution for neutralization. What is the molarity of the NaOH solution?

Problem #3What Volume of 0.150M HNO3 solution is needed to

neutralize 45.0mL of a 0.550M KOH solution?Given: MA = 0.150 MB = 0.550M VA = ? VB = 45mLSolution1.

Problem#4

How many mL of 0.2056M NaOH is required to completely

How important is pH in living things?

pH plays an important role

Most living organisms survive in a narrow pH

Ex: human blood is maintained between 7.35 to 7.45 by buffering system

Buffers

resist a change in pH even when a strong acid or base is added to itContains

--->weak acid and its conjugate base weak base and its conjugate acid

Note:

Buffers has a remarkable property of maintaining an almost constant pH even with the addition of a strong base or acid due to the presence of the weak acid that neutralizes any added base and also a weak base that neutralizes any added acid.

Ex:

1M CH3COOH and 1M NaCH3OO

acetic Sodium acid acetateAdded w/ a base CH3COOH + OH- ---> H2O + CH3COO-

Added w/ an acid CH3COO + H3O+ --> H2O + CH3COOH

Note: acetate ion will neutralize any added acid

What happens if the blood becomes basic or acidic?

The bicarbonate-carbonic acid ( HCO3/H2CO3) buffer will buffer the

blood.If it becomes basic, the carbonic acid

will neutralize the OH- ions If it becomes acidic, the bicarbonate

will neutralize the H3O+.