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buffers

weak acids or conjugate bases that can react with strong acids or bases to prevent sharp, sudden changes in pH

antifreeze

Ethylene Glycol, A chemical that is mixed with water and added to the cooling system of a car. It moves through the engine to remove extra heat.

carbonic acid

a compound with the formula H2CO3 that results from the combination of carbon dioxide (CO2) and water (H2O); of particular importance in maintaining the body's acid-base balance.

acidosis

abnormally high acidity (excess hydrogen-ion concentration) of the blood and other body tissues

hemaglobin

an ion containing protein that transports the bulk of oxygen that is carried in the blood

hyperventilate

To provide ventilations at a higher rate than normal.

carbonic acid neutralize base

what is happenining here

true

a weak acid by itself isnt strong enough to be a buffer and vice versa for weak bases

a weak acid and its conjagate base

what must a buffer contain significant amounts of

it will neutralize only if the strong base is amount is less

what would occur to the solution

common ion effect

The phenomenon in which the addition of an ion common to two solutes brings about precipitation or reduced ionization, Ex: AgCl in water

If you add in NaCl (more Cl ion) then LESS solid will dissolve at equilbirum

Application of Le Chatelier

DECREASES solubility

...

write the three equations

H H equation

an equation that allows use to quickly find the ph of a buffer from the initial morality only if x is small

henderson haselbach equation

pH = pKa + log ([A-]/[HA])

[A-] concentration of conjugate base
[HA] concentration of acid

Ka = dissociation constant

pka

-logka, acid dissociation constant

A buffer is a solution that is resistant to changes in pH. Buffers work by converting strong acids or bases into weak acids or bases.

Consider a buffer that contains a weak acid (HA) and its conjugate base (A-). If we add a strong acid like HCl, or a strong base like NaOH, the reactions that occur are as follows

HCl(aq) + A-(aq) ® HA(aq) + Cl-(aq)

NaOH(aq) + HA ® H2O(l) + A-(aq)

2) What is a buffer? How does a buffer work? How does it neutralize added acid? Added base?

4) The Henderson-Hasselbach equation is

pH = pKa + log10{[base]/[acid]}

It is useful in preparing a buffer solution with a particular value for pH.

4) What is the Henderson-Hasselbalch equation and why is it useful?

...

27) In which of these solutions will HNO2 ionize less than it does in pure water?
a) 0.10 M NaCl b) 0.10 M NaOH
c) 0.10 M KNO3 d) 0.10 M NaNO2

d

1) Which of the following reactions will go essentially to completion?
a) Reaction of a strong acid with a strong base
b) Reaction of a strong acid with a weak base
c) Reaction of a weak acid with a weak base
d) Both a and b
e) Both a and b and c

e

2) Which of the following aqueous solutions would be a buffer solution?
a) A solution that has 0.100 M HNO2 (a weak acid) and 0.100 M NO2-
b) A solution that has 0.100 M HClO4 (a strong acid) and 0.100 M ClO4-
c) A solution that has 0.100 M NH3 (a weak base) and 0.100 M NH4+
d) Both a and b
e) Both a and c

a

3) Consider the titration of H3PO4, a weak polyprotic acid, with Ba(OH)2, a strong base. The number of equivalence points that will be observed in this titration is
a) 3
b) 2
c) 1
d) 0
e) None of the above

a. weak acid, strong base
b.point B
c.point C
d.o-cresonphthalein pKa = 9.0

1) The following questions refer to the titration curve given below. For each of the following questions circle the correct answer. There is one and only one correct answer per question. [3 points each]

a) The titration curve shows the titration of

a strong acid a weak acid a strong base a weak base
with a strong base with a strong base with a strong acid with a strong acid

b) Which point on the titration curve represents a region where a buffer solution has formed?

point A point B point C point D

c) Which point on the titration curve represents the equivalence point?

point A point B point C point D

d) Which of the following would be the best indicator to use in the titration?

erythrosin B methyl red bromthymol blue o-cresonphthalein
pKa = 2.9 pKa = 5.4 pKa = 6.8 pKa = 9.0

2) Define the following terms [4 points each]

a) endpoint

The point in a titration where the indicator being used changes color. One tries to choose an indicator whose end point is as close as possible to the equivalence point of the titration.

2) Define the following terms [4 points each]

a) endpoint

b) selective precipitation

The process where a substance is added to a solution that causes one solute in the solution to form a solid (precipitate) while the remaining solutes remain in solution. The precipitate can then be removed by filtration. Selective precipitation therefore is a method that can separate a particular solute from a mixture of solutes in a solution.

2) Define the following terms [4 points each]
b) selective precipitation

For a buffer, pH = pKa + log10{[base]/[acid]}

But [acid] = 2 [base], and so

pH = - log10(1.8 x 10-4) + log10 (1/2) = 3.44

3) A buffer solution is formed using formic acid (HCOOH, Ka = 1.8 x 10-4) and formate ion (HCOO-). The concentration of formic acid in the buffer solution is twice the concentration of formate ion. What is the pH of the buffer solution? [4 points]

pH = pKa + log10{[base]/[acid]}

and so
log10{[base]/[acid]}= pH - pKa = 7.40 - {- log10(2.9 x 10-8)} = - 0.138

and so (taking the inverse log10 of both sides of this equation)

{[base]/[acid]} = 10-0.138 = 0.728

[base] = 0.728 [acid] = 0.728 (0.2000 M) = 0.1457 M

Since potassium hypochlorite is a strong electrolyte (completely ionizes in water), then

moles KClO = 1.000 L 0.1457 mol = 0.1457 mol
1.000 L

grams KClO = 0.1457 mol 90.55 g = 13.2 g
1.00 mol
,

1) A chemist has a 0.2000 M stock solution of hypochlorous acid (HClO, a weak acid, with Ka = 2.9 x 10-8) and solid potassium hypochlorite (KClO, M = 90.55 g/mol), a strong electrolyte containing the conjugate base of hypochlorous acid. How many grams of KClO must be added to 1.000 L of the stock HClO solution to form a buffer solution with pH = 7.40? You may assume that the volume of the solution does not change when KClO is added. [12 points]

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