Question 1

Which of the following best explains why sodium (Na) and chlorine (Cl) combine to form sodium chloride (NaCl) with properties very different from the original elements?

Accepted Answer

NaCl is formed by an ionic bond, where sodium donates an electron to chlorine, resulting in emergent properties.

Question 2

A plant is growing in soil that is deficient in nitrogen. According to Liebig's Law of the Minimum, what will most likely happen to the plant's yield?

Accepted Answer

The plant's yield will be limited by the nitrogen deficiency, regardless of the abundance of other nutrients.

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 4

A radioactive isotope is used in a PET scan to detect cancerous tissue. What property of radioactive isotopes makes this possible?

Accepted Answer

They decay spontaneously, emitting particles and energy that can be traced.

Question 5

Which of the following best 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 6

Calculate the number of neutrons in an atom of sodium with a mass number of 23 and an atomic number of 11.

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 7

Which property of water allows a spider to walk on its surface, as shown in the image?

Accepted Answer

Cohesion due to hydrogen bonding, resulting in high surface tension

Question 8

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice are more ordered, making ice less dense than liquid water.

Question 9

Which of the following best explains why water is an excellent solvent for ionic and polar substances?

Accepted Answer

Water is a polar molecule, allowing it to interact with and dissolve ionic and polar substances.

Question 10

A solution has a pH of 4. What is the concentration of hydrogen ions ($$[H^+]) in $$the solution?

Accepted Answer

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

Question 11

Which of the following is an example of a trace element required by humans, and what is a consequence of its deficiency?

Accepted Answer

Iodine; deficiency causes goiter

Question 12

Which process describes the use of plants like sunflowers to remove toxic heavy metals from contaminated soils?

Accepted Answer

Phytoremediation

Question 13

What type of chemical bond is formed when two atoms share a pair of electrons?

Accepted Answer

Covalent bond

Question 14

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 15

Which of the following is a real-life application of van der Waals interactions?

Accepted Answer

The ability of geckos to walk on walls due to numerous weak interactions between their feet and surfaces.

Question 16

Which property of water is most directly responsible for the transport of water against gravity in plants?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 17

If a solution changes from pH 7 to pH 5, how does the hydrogen ion concentration change?

Accepted Answer

It increases by a factor of 100

Question 18

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in the concentrations of $$H^+$$ and $$OH^-$$ ions.

Question 19

Which of the following is true about the energy levels of electrons in an atom?

Accepted Answer

Electrons can move to higher energy levels by absorbing energy.

Question 20

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil molecules are nonpolar and do not interact favorably with polar water molecules.

Chapter 2: The Chemical Context of Life – Study Notes

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