Question 1

Which of the following best describes the difference between kinetic energy and potential energy in biological systems?

Accepted Answer

Kinetic energy is the energy of motion, such as heat or light, while potential energy is stored energy due to position or structure, such as in chemical bonds.

Question 2

Which six elements make up about 99% of all living tissue by dry weight?

Accepted Answer

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur

Question 3

An atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 5

Which of the following best explains why noble gases are chemically inert?

Accepted Answer

They have a full outer electron shell, making them stable and unlikely to form chemical bonds.

Question 6

What is the maximum number of electrons that can occupy the second electron shell of an atom?

Accepted Answer

$$8$$

Question 7

Which of the following best describes an ionic bond?

Accepted Answer

A strong electrostatic force between oppositely charged ions.

Question 8

If an atom has 7 electrons in its outer shell, what is its most likely behavior in forming chemical bonds?

Accepted Answer

It will tend to gain 1 electron to achieve a stable octet.

Question 9

Which of the following statements about covalent bonds is true?

Accepted Answer

Covalent bonds involve the sharing of electron pairs between atoms.

Question 10

Which of the following best explains why water molecules are polar?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing an unequal sharing of electrons and resulting in partial charges.

Question 11

Which of the following is a correct statement about hydrogen bonds?

Accepted Answer

Hydrogen bonds are weak interactions between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 12

Which of the following pairs of elements would most likely form a nonpolar covalent bond?

Accepted Answer

C and C

Question 13

A molecule of methane ($$CH_4) $$contains how many covalent bonds, and what is the arrangement of these bonds?

Accepted Answer

$$4$$ covalent bonds arranged tetrahedrally around the carbon atom

Question 14

Which of the following best describes the trend of electronegativity (EN) on the periodic table?

Accepted Answer

EN increases as you move up a group and to the right across a period.

Question 15

Which of the following is the best example of a polar covalent bond in a biological molecule?

Accepted Answer

O–H

Question 16

A student is given a sample of an unknown element. It has 8 protons, 8 neutrons, and 8 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number $$= 8$$, Mass number $$= 16$$

Question 17

Which of the following best explains why ionic compounds tend to form crystalline solids at room temperature?

Accepted Answer

The strong electrostatic attraction between oppositely charged ions arranges them in a repeating, orderly pattern.

Question 18

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons determine the chemical reactivity and bonding behavior of an atom.

Question 19

Which of the following best describes the octet rule?

Accepted Answer

Atoms are most stable when they have eight electrons in their outermost shell.

Question 20

Which of the following is a correct statement about the relationship between atomic number and the number of protons in an atom?

Accepted Answer

The atomic number is equal to the number of protons in the atom.

Lab 1 Chem Review

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