L2: pH Measurement and Buffer Preparation

pH

a measure of how acidic/basic a solution is.

0-14

pH range goes from ___ __to__ __

acidic

If pH < 7, then the solution is __________

neutral

If pH = 7, then the solution is _______________

**basic**

If pH > 7, then the solution ______________

C

A solution has a pH of 9. What can be inferred about the nature of this solution?

A) The solution is acidic.

B) The solution is neutral.

C) The solution is basic.

D) The solution is both acidic and basic.

A

A solution has a pH of 4.5. What does this pH value indicate about the solution?

A) The solution is acidic.

B) The solution is neutral.

C) The solution is basic.

D) The solution is neither acidic nor basic.

potential of hydrogen

The letters pH stand for _______________

pH

_______ is a measure of the hydrogen ion (H+) concentration in an aqueous solution

pH

__________ is also expressed as the negative of base 10 logarithm of the hydrogen-ion concentration.

potential of Hydroxide

pOH stands for _________________

\-log \[H+\]

pH = formula

\-log \[OH-\]

pOH = formula

pOH

It is a measure of hydroxide ion (OH–) concentration

pOH

It is expressed as the negative of the base 10 logarithm of the hydroxide-ion concentration.

7\.8-8.4

Nemo (clownfish) requires a pH between ________________

chemical reactions and processes are affected by the hydrogen ion concentration

The control of pH is important in organism and their cells because ____________________

acid

a compound that can donate a hydrogen ion.

base

a substance that accepts hydrogen ions.

hydrogen

low pH; Acids

hydroxide

high pH; Alkalis

B

What does the pH value represent in an aqueous solution?

A) The concentration of hydroxide ions (OH-)

B) The concentration of hydrogen ions (H+)

C) The concentration of oxygen ions (O2-)

D) The concentration of sodium ions (Na+)

D

What does the term "pOH" represent in a solution?

A) The concentration of hydrogen ions (H+)

B) The concentration of hydroxide ions (OH-)

C) The negative logarithm of the hydrogen-ion concentration

D) The negative logarithm of the hydroxide-ion concentration

6

Approx ___ mmol of H+ is produced by metabolism everyday

4; 100000

Approx 6mmol of H+ is produced by metabolism everyday if all of this were to be diluted in the extracellular fluid \[ECF\] (=14L), \[H+\] would be __mmol/L , or__ __ times ==**more acidic than normal!**==

TRUE

Efficient urine excretion of H+ produced ensures that this does not happen; as a result, urine is profoundly acidic.

\
T/F

Carbon dioxide (CO2).

Metabolism also produces ________________.

H2CO3, carbonic acid

In solution the CO2 converts to weak acid (H2CO3, ___________).

acid-base balance

The large amount of CO2 produced by cellular activity each day could upset __________________

lungs

But under normal circumstances large amount of CO2 is to be excreted via _______.

B

Approximately how many millimoles (mmol) of H+ ions are produced by metabolism every day?

A) 60 mmol

B) 6 mmol

C) 600 mmol

D) 16 mmol

B

What is the primary reason for the excretion of carbon dioxide (CO2) via the lungs, which is produced as a result of metabolism?

A) To increase the oxygen content in the bloodstream

B) To prevent the buildup of carbonic acid (H2CO3) in solution

C) To enhance the production of bicarbonate ions (HCO3-) in the blood

D) To lower the overall acidity of the body's extracellular fluid

Chemists

_____________ have tried to define acids and bases in relation to their compositions and molecular structures

Svante Arrhenius

defines **acids** as substances that produce H+ ions in aqueous solution while **bases** are substances that produce OH- ions in aqueous solution

Gilbert N. (G.N.) Lewis

Mentioned that **acids** are electron-pair acceptors and **bases** are electron-pair donor.

Johannes Bronsted and Thomas Lowry

the most useful and accepted definition of acids and bases nowadays are those proposed by ____________ __and__ __________________

Bronsted-Lowry theory

the most useful and accepted definition of acids and bases nowadays are those proposed by Johannes Bronsted and Thomas Lowry, and it is known as the _______________

acid

HCl (Hyrochloric acid) is an _______ because it donates a proton making Cl- (Chloride)

base

water is a ____ because it accepts a proton making H3O+.

Bronsted-Lowry theory

the theory explains that for every acid-base reaction, there is a creation of conjugate acid-base pair.

TRUE

Cl- is the conjugated base of HCl and H3O+ is the conjugated acid of water as shown below.

\
T/F

Soren Peter Lauritz Sorensen (S.P.L.) Sorensen

introduced the pH scale that measures the strength of an aqueous acidic or basic solution.

pH = -log \[H+\]

It converts the H+ concentrations to pH using the formula.

pH

The precise definition of _______ is "the negative common logarithm of the activity of hydrogen ion in solution

C

According to the definition, how are acids and bases distinguished based on their behavior in aqueous solutions?

A) Acids produce OH- ions, while bases produce H+ ions.

B) Acids and bases both produce H+ ions.

C) Acids produce H+ ions, while bases produce OH- ions.

D) Acids and bases both produce OH- ions

A

In the given rationale, why is HCl considered an acid?

A) HCl donates a proton, forming Cl- (Chloride).

B) HCl accepts a proton, forming Cl- (Chloride).

C) HCl donates an electron, forming Cl- (Chloride).

D) HCl releases an electron, forming Cl- (Chloride)

A

According to the rationale, what is the conjugated base of HCl?

A) Cl-

B) HCl

C) H3O+

D) OH-

C

Which mathematical expression represents the calculation of pH using the hydrogen ion concentration \[H+\]?

A) pH = \[H+\]

B) pH = log \[H+\]

C) pH = - log \[H+\]

D) pH = 10^-\[H+\]

A

If a solution has a pH of 6.75, what is the pOH of the solution?

A) pOH = 7.25

B) pOH = 7.30

C) pOH = 7.75

D) pOH = 7.80

Buffers

________ prevent changes in pH

Buffers

__________ resist changes in the pH even when acids or bases are added.

**Buffers**

**_______ are a** **mixture of a weak acid or alkali and one of its salts**

Le Chatellier's principle.

The ability of buffers to resist large changes in pH is governed by the ________________

La Chatellier's Principle

A principle of equilibrium shift due to changes in buffer conditions.

carbonic acid

In our blood, ____________ is the most important buffer.

carbonic acid

This solution maintains our blood pH to facilitate transport of oxygen from the lungs to the cells

C

What is the primary role of buffers in a solution?

A) To increase the pH of the solution

B) To decrease the pH of the solution

C) To prevent changes in pH

D) To enhance the reactivity of the solution

D

How do buffers resist changes in pH when acids or bases are added to a solution?

A) By neutralizing the acids or bases

B) By releasing hydrogen ions (H+) or hydroxide ions (OH-)

C) By converting the acids or bases into water

D) By maintaining a balance between weak acid and its conjugate base

D

**How does carbonic acid function as a crucial buffer in our blood, and what role does it play in maintaining blood pH?**

**A) Carbonic acid helps in digestion by breaking down complex molecules.**

**B) Carbonic acid supports bone health by facilitating calcium absorption.**

**C) Carbonic acid prevents the accumulation of lactic acid during exercise.**

**D) Carbonic acid maintains blood pH to enable efficient oxygen transport from the lungs to the cells.**

Litmus Test

a simple test to check if a substance is acidic or basic using a _________ paper

acidic

Blue litmus paper turns red for _______ pH

basic

Red litmus paper turns blue for _______ pH

neutral

No color change for ___________ pH

Indicator paper

is impregnated with organic compounds that change their color at different pH values.

Indicator paper

The color shown by the paper is then compared with a color standard usually provided by the manufacturer.

pH meter

should be calibrated first before being operating the device

pH 7, pH 4, and pH 10

The standard procedure for calibrating a pH meter is to calibrate it at three different pHs (pH ___, pH _, and pH _).

electrodes

After calibration, all that needs to be done is to insert the ___________ of the pH meter into the solution to be tested and read the pH flashed on the screen.