All about pH pOH H+ OH-, Exercises of Biochemistry

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Acids, Bases,

pH and pOH calculations,

and Equilibria in

Acid-Base Solutions

ERIC D. ALINA, LPT Instructor II College of Arts, Sciences, and Education (CASE) University of Santo Tomas – Legazpi

The Legazpi Thomasian Prayer

Lord, in our weakness and vulnerability, bless us with your grace to soar beyond limits. Enlighten our vision and guide our mission that we may clearly see and fully realize our quest. Keep our passion for the truth burning and our compassion for humanity bright that we may live truly and lovingly. Keep us in harmony with the universe that we may be joyfully one with your creation. Yet above and before all, Lord, grant us the grace to love you with all our mind and soul and with all our heart and strength that we may praise, bless, and preach according to your will. Make us, Legazpi Thomasians, whole as a person, and as a community in your wondrous name, this we ask and pray with a happy and grateful memory. Amen.

LEARNING OBJECTIVES

At the end of this lesson, you must be able to: e. describe buffer systems; f. calculate pH, pOH, and molar concentrations of acid and bases and their conjugates using Henderson-Hasselbalch equations; g. define buffer capacity and buffer range; and h. calculate buffer capacity of buffer systems

The pH

The pH

Low pH corresponds to high concentrations of 𝑯

and

high pH values correspond to low concentration of

It is also directly related to the ratio of 𝑯

and

−

in solutions.

The pH

Source: Masterton, W. L., & Hurley, C. N. (2015). Chemistry: principles and reactions. Cengage Learning.

The Acid-Base Balance in the Human Body

The pH of the human body ranges between 7. 35 to 7. 45 , with the average at 7. 40 , in the absence of pathological states. This pH level is ideal for many biological processes, one of the most important being the oxygenation of blood.

The Acid-Base Balance in the Human Body

Acidosis – is caused by an overproduction of acid that builds up in the blood or excessive loss of bicarbonate from the blood (metabolic acidosis) or by a buildup of carbon dioxide in the blood the results from poor lung function or depressed breathing (respiratory acidosis). Source: https://en.wikipedia.org/wiki/Acidosis

Acidemia – is an increase in the hydrogen ion concentration of the blood, resulting in a decrease in pH. Alkalemia – is a decrease in the hydrogen ion concentration in the blood, resulting in an increase in pH.

The Acid-Base Balance in the Human Body

pH Determination/Measurement

Colorimetric Method – is based on the property of acid-base indicator dyes, which produce color depending on the pH of the sample. The color change can be measured as an absorbance change spectrophotometrically.

Colorimetric Method of pH Determination

Source: https://theconstructor.org/environmental-engg/ph-of-water/19855/

Colorimetric Method of pH Determination

Source: https://theconstructor.org/environmental- engg/ph-of-water/ 19855 / Source: https://byjus.com/chemistry/litmus-paper/

Titrate a weak acid using an indicator that changes under slightly alkaline solutions. Titrate a weak base using an indicator that changes color at a slightly acidic pH. When titrating strong acids or bases, aim for a pH indicator that displays color change near a neutral pH.

Colorimetric Method of pH Determination

Source: https://science notes.org/ph- indicator- chart-colors- and-ranges/