Q: A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$the solution? Use the formula $$pH = -\log_{10}[H^+].$$

$$[H^+] = 1 \times 10$$^{-4}$$ \ M$$

Question 1

Which subatomic particle determines the atomic number of an element and is responsible for its unique chemical identity?

Accepted Answer

Proton

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is commonly used in biological research. Which of the following best describes why $$^{14}C is $$useful in tracing metabolic pathways?

Accepted Answer

$$^{14}C is $$chemically identical to $$^{12}C$$ but can be detected due to its radioactivity.

Question 3

Why do elements in the same group of the periodic table have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 4

Which of the following best distinguishes a molecule from a compound?

Accepted Answer

A molecule is a group of atoms bonded together, which can be the same or different elements; a compound is a molecule made of different elements.

Question 5

Which of the following is an example of an ionic bond in a biological context?

Accepted Answer

The bond between sodium and chloride ions in table salt ($$NaCl).$$

Question 6

Which property of water allows it to move upward through the stem of a plant against gravity?

Accepted Answer

Cohesion and adhesion (capillary action)

Question 7

Hydrogen bonds are important in biological systems because they:

Accepted Answer

Allow water to dissolve many substances and stabilize large molecules like DNA.

Question 8

How does the polarity of water molecules contribute to their ability to dissolve ionic compounds like $$NaCl$$?

Accepted Answer

The positive and negative ends of water molecules surround and separate the ions.

Question 9

A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$the solution? Use the formula $$pH = -\log_{10}[H^+].$$

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$ \ M$$

Question 10

Which of the following best describes the function of a buffer in a biological system?

Accepted Answer

A buffer resists changes in pH by accepting or donating hydrogen ions.

Question 11

A patient’s blood pH drops from 7.4 to 7.1. How does the bicarbonate buffer system respond to this change?

Accepted Answer

It absorbs excess $$H^+$$ ions to raise the pH back toward normal.

Question 12

Which of the following scenarios best illustrates capillary action in nature?

Accepted Answer

Water moving up a thin glass tube or through plant xylem.

Question 13

Which of the following is NOT a unique property of water that supports life?

Accepted Answer

Low surface tension

Question 14

If a molecule has polar covalent bonds, what does this imply about the sharing of electrons between atoms?

Accepted Answer

Electrons are shared unequally, resulting in partial charges.

Question 15

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice create an open lattice, making it less dense than liquid water.

Question 16

Which of the following best describes the relationship between acids, bases, and pH?

Accepted Answer

Acids increase $$[H^+]$$ and lower pH; bases increase $$[OH^-]$$ and raise pH.

Question 17

Which of the following is a real-life example of a covalent bond in a biological molecule?

Accepted Answer

The bond between two hydrogen atoms in a hydrogen gas molecule ($$H_2).$$

Question 18

A solution is described as a strong base. Which of the following pH values is most likely for this solution?

Accepted Answer

pH = 13

Question 19

Which of the following best explains why water has a high specific heat capacity?

Accepted Answer

Hydrogen bonds between water molecules require more energy to break.

Question 20

Which of the following best explains why the structure of a molecule determines its function in biological systems?

Accepted Answer

The structure determines how the molecule interacts with other molecules and fits into biological processes.

General Biology: Atomic Structure, Chemical Bonds, Water Properties, and Biological Systems

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