Question 1

Which of the following best explains why sodium chloride (NaCl) has properties different from both sodium and chlorine?

Accepted Answer

The emergent properties of NaCl result from the fixed ratio and chemical bonding between sodium and chlorine atoms.

Question 2

Which of the following elements makes up the largest percentage of the human body by mass?

Accepted Answer

Oxygen

Question 3

A radioactive isotope of carbon ($$^{14}C) is $$used in PET scans to track metabolism. What property of $$^{14}C$$ makes it useful for this purpose?

Accepted Answer

It emits particles and energy that can be detected by imaging instruments.

Question 4

Which statement correctly describes the difference between atomic number and mass number?

Accepted Answer

Atomic number is the number of protons; mass number is the sum of protons and neutrons.

Question 5

If an atom 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 6

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of a pair of valence electrons between two atoms.

Question 7

What is the main reason noble gases are chemically inert?

Accepted Answer

They have a full valence electron shell.

Question 8

Which of the following is true about isotopes?

Accepted Answer

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

Question 9

Which equation correctly represents the photosynthesis reaction described in the study materials?

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 10

A sodium atom ($$Na) $$loses one electron to become a sodium ion ($$Na^+). $$What type of bond does it form with a chloride ion ($$Cl^-$$)?

Accepted Answer

Ionic bond

Question 11

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 12

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions involve both the making and breaking of chemical bonds.

Question 13

What is chemical equilibrium?

Accepted Answer

The point at which the forward and reverse reactions occur at the same rate.

Question 14

Which of the following is an example of a trace element required by humans?

Accepted Answer

Iron

Question 15

Which of the following best explains why van der Waals interactions can be strong in some biological contexts?

Accepted Answer

Collectively, many weak van der Waals interactions can create a strong overall attraction, such as between a gecko's toe hairs and a wall.

Question 16

Which of the following statements about electron shells is correct?

Accepted Answer

Electrons in shells farther from the nucleus have higher potential energy.

Question 17

Which of the following molecules contains a polar covalent bond?

Accepted Answer

$$H_2O$$

Question 18

A molecule's shape is primarily determined by:

Accepted Answer

The positions of its atoms' orbitals and the hybridization of those orbitals.

Question 19

Which of the following best describes the role of valence electrons in chemical bonding?

Accepted Answer

Valence electrons are in the outermost shell and determine the chemical behavior of an atom.

Chapter 2: The Chemical Context of Life – Study Notes

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