Chemistry: The pH Scale and Buffers

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Questions and Answers

What defines potential energy?

Energy that is actively causing movement

Energy stored and capable of doing work (correct)

Energy that cannot be transformed

Energy involved in rapid reactions

What does a neutral solution have on the pH scale?

pH of 10

pH of 14

pH of 0

pH of 7 (correct)

Which statement about acids is accurate?

Acids are neutral substances

Acids donate protons (correct)

Acids have a pH greater than 7

Acids are proton acceptors

What occurs when products contain more potential energy than reactants?

Energy must be added for the reaction Signup and view all the answers

How does temperature affect the rate of a chemical reaction?

Higher temperatures generally speed up reactions Signup and view all the answers

What happens during a change of one unit on the pH scale?

It represents a 10-fold change in H+ concentration Signup and view all the answers

Which of the following statements is true regarding bases?

Bases are proton acceptors Signup and view all the answers

What is true about the relationship between pH number and H+ concentration?

Lower pH indicates higher H+ concentration Signup and view all the answers

What is the normal pH range for human blood?

7.35 to 7.45 Signup and view all the answers

What condition results when blood pH drops below 7.35?

Acidosis Signup and view all the answers

How does the concentration of reactants affect the rate of a chemical reaction?

Higher concentration increases the likelihood of reaction. Signup and view all the answers

What happens to the rate of chemical reactions during a fever?

It increases. Signup and view all the answers

What is the role of buffers in a solution?

They resist changes in pH. Signup and view all the answers

What is a characteristic of Carbon Dioxide (CO2)?

It is a waste product from metabolism. Signup and view all the answers

Which statement best describes water in terms of its molecular structure?

It consists of one oxygen atom and two hydrogen atoms joined by polar covalent bonds. Signup and view all the answers

How does the body maintain pH homeostasis?

Through the action of buffers. Signup and view all the answers

Which of the following is NOT a role of water in living organisms?

Regulating blood pressure Signup and view all the answers

What distinguishes inorganic molecules from organic molecules?

Organic molecules contain carbon Signup and view all the answers

Which of the following groups are NOT considered major organic molecules essential for living organisms?

Minerals Signup and view all the answers

What mechanism contributes to the diversity of organic molecules?

Variation in carbon chain lengths Signup and view all the answers

Which statement about inorganic substances is true?

They play roles in human anatomy and physiology Signup and view all the answers

Which combination of atoms can form the carbon framework in large molecules?

Various atoms including hydrogen and oxygen Signup and view all the answers

How did the understanding of organic and inorganic substances evolve with time?

Organic substances can be synthesized in laboratories Signup and view all the answers

Which of the following elements is critical in forming covalent bonds that make up organic molecules?

Carbon Signup and view all the answers

What is the composition of carbohydrates?

Carbon, hydrogen, and oxygen Signup and view all the answers

Which of the following statements about phospholipids is true?

The phosphate head is hydrophilic and water-soluble Signup and view all the answers

Which group of organic molecules is NOT one of the four major groups essential to living organisms?

Minerals Signup and view all the answers

What type of molecule are monosaccharides classified as?

Simple sugars Signup and view all the answers

Eicosanoids are derived primarily from which type of molecule?

Fatty acids Signup and view all the answers

What type of bond joins disaccharides?

Covalent bond Signup and view all the answers

In the context of lipids, which characteristic describes the nonpolar end of a phospholipid?

Hydrophobic and lipid-soluble Signup and view all the answers

What type of carbohydrate consists of many monosaccharides linked together?

Polysaccharides Signup and view all the answers

What is the primary function of amino acids in the body?

To regulate chemical reactions and form body tissues Signup and view all the answers

Which of the following best describes enzymes?

Protein catalysts that increase chemical reaction rates Signup and view all the answers

What composes the building blocks of nucleic acids?

Nucleotides made of sugar, nitrogenous base, and a phosphate group Signup and view all the answers

Which sugar is found in ribonucleic acid (RNA)?

Ribose Signup and view all the answers

Which of these molecules serves as the energy currency of cells?

ATP (adenosine triphosphate) Signup and view all the answers

What type of molecule is DNA primarily composed of?

Nucleotides containing deoxyribose, organic bases, and phosphates Signup and view all the answers

Which of the following is a characteristic of essential amino acids?

They must be obtained from dietary sources Signup and view all the answers

Which of the following pairs are classified as double-ringed organic bases?

Adenine and guanine Signup and view all the answers

Study Notes

The pH Scale

Indicates the concentration of hydrogen ions (H+) in a solution
Scale ranges from 0 to 14
A neutral solution has a pH of 7.0 (H+ = OH-)
An acidic solution has a pH less than 7.0 (H+ > OH-)
A basic or alkaline solution has a pH greater than 7.0 (H+ < OH-)
The pH number and H+ concentration are inversely related: the lower the pH, the higher the H+ concentration
A change of one unit on the pH scale represents a 10-fold change in the H+ concentration
Normal pH range for human blood is 7.35 to 7.45
Acidosis occurs when blood pH drops below 7.35
Alkalosis occurs when blood pH rises above 7.45

Salts

A compound consisting of a positive ion other than H+ and a negative ion other than OH-
Formed by the reaction of an acid and base

Buffers

A chemical that resists pH changes when either an acid or base is added to a solution
When an acid is added to a buffered solution, the buffer binds to H+, preventing a decrease in pH
Important for maintaining homeostasis by keeping body fluid pH within a narrow range

Oxygen and Carbon Dioxide

Oxygen (O2)
- Small, nonpolar, inorganic molecule
- Consists of two oxygen atoms bound by a double covalent bond
- Essential for most living organisms
Carbon Dioxide (CO2)
- Consists of one carbon atom and two oxygen atoms
- Produced when food molecules (e.g., glucose) are metabolized within cells
- Eliminated as a metabolic by-product and exhaled during respiration

Water

Inorganic molecule consisting of an oxygen atom joined by polar covalent bonds to two hydrogen atoms
Essential for survival and plays crucial roles:
- Stabilizing body temperature
- Providing protection
- Facilitating chemical reactions
- Transporting substances

Organic Molecules

Contain carbon
Carbon atoms bound together by covalent bonds form the framework of many large molecules
Variety in molecules due to:
- Variation in the length of carbon chains
- Combination of atoms bound to the carbon framework

Major Organic Molecules Essential to Life

Carbohydrates
Lipids
Proteins
Nucleic Acids (DNA & RNA)

Carbohydrates

Composed of carbon, hydrogen, and oxygen atoms
Smallest carbohydrates are monosaccharides (simple sugars)
Disaccharides: formed when two monosaccharides are joined
Polysaccharides: consist of many monosaccharides bound in long chains

Lipids

Composed of carbon, hydrogen, and oxygen but with a lower proportion of oxygen than carbohydrates
Insoluble in water but soluble in organic solvents such as ether or alcohol
Include:
- Fats
- Phospholipids
- Eicosanoids
Fats
- Saturated: contain only single covalent bonds between carbon atoms (butter, lard, and animal fat)
- Unsaturated: contain one or more double covalent bonds between carbon atoms (olive oil, peanut oil, and vegetable oils)
- Polyunsaturated: contain two or more double covalent bonds (safflower, sunflower, corn, and fish oils)
Phospholipids
- Important structural components of cell membranes
- Contain a phosphate head (hydrophilic) and two fatty acid chains (hydrophobic)
Eicosanoids
- Regulatory molecules derived from fatty acids
- Important in inflammation and blood clotting

Proteins

Large molecules that contain carbon, hydrogen, oxygen, and nitrogen
Made up of building blocks called amino acids
The body can synthesize 12 amino acids, but the other 8, called essential amino acids, must be obtained from the diet.
Important functions include:
- Regulation of chemical reactions
- Providing framework for tissues
Enzymes: protein catalysts that increase the rate of chemical reactions without being permanently changed

Nucleic Acids: DNA & RNA

Large molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus
Consists of building blocks called nucleotides
Each nucleotide contains a sugar (monosaccharide), a nitrogenous base, and a phosphate group
DNA contains deoxyribose as its sugar, while RNA contains ribose.
Organic Bases:
- Single-ringed molecules: Thymine, cytosine, and uracil
- Double-ringed molecules: Adenine and guanine
Deoxyribonucleic Acid (DNA)
- The genetic material of cells
- Copies of DNA are transferred from one generation of cells to the next
- Contains information that determines the structure of proteins
Ribonucleic Acid (RNA)
- Plays a crucial role in protein synthesis

Adenosine Triphosphate (ATP)

Consists of adenosine (the sugar ribose with the base adenine) and three phosphate groups
Often called the energy currency of cells because it can both store and provide energy

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Description

Explore the concepts of the pH scale, salts, and buffers in this chemistry quiz. Understand how pH affects solutions and the importance of buffers in maintaining stable pH levels. Delve into the implications of pH on human health as well.