When a substance undergoes a chemical change. What is a chemical reaction?
Agenda 5-13-07 Do Now : 1.write the products of the reaction when the reactants given below...
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Transcript of Agenda 5-13-07 Do Now : 1.write the products of the reaction when the reactants given below...
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 reaction
A 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 with
all 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 L
3.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 = 45mL
Solution
1.
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 it
Contains
--->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 acetate
Added 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+.