Question 1

Which of the following statements best explains why the properties of a compound such as formic acid differ from those of its constituent elements?

Accepted Answer

Compounds are substances consisting of two or more elements in a fixed ratio, resulting in emergent properties different from those of the elements.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Carbon, hydrogen, oxygen, and nitrogen

Question 3

A radioactive isotope of carbon ($$^{14}\mathrm{C}) is $$used in radiometric dating. If the half-life of $$^{14}\mathrm{C} is 5$$,730 years, how much of a 100 g sample would remain after 11,460 years?

Accepted Answer

$$25\ \mathrm{g}$$

Question 4

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 5

Why are radioactive isotopes useful as tracers in medical imaging?

Accepted Answer

They decay spontaneously, emitting particles and energy that can be detected by imaging instruments.

Question 6

Which statement about electron shells and energy levels is correct?

Accepted Answer

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

Question 7

What determines the chemical behavior of an atom?

Accepted Answer

The distribution of electrons in the electron shells, especially the valence shell

Question 8

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 9

In a water molecule ($$\mathrm{H}_2\mathrm{O}$$), the oxygen atom is more electronegative than the hydrogen atoms. What type of bond is formed between the oxygen and hydrogen atoms?

Accepted Answer

Polar covalent bond

Question 10

Which of the following is true about ionic bonds?

Accepted Answer

They result from the attraction between oppositely charged ions.

Question 11

Which of the following interactions is responsible for the ability of a gecko to climb smooth surfaces?

Accepted Answer

Van der Waals interactions

Question 12

Why are weak chemical interactions, such as hydrogen bonds and van der Waals interactions, important in biological systems?

Accepted Answer

They allow large biological molecules to maintain their functional forms and enable reversible interactions.

Question 13

Which of the following best explains why opiates and endorphins can have similar effects in the human brain?

Accepted Answer

They have similar molecular shapes, allowing them to bind to the same receptors.

Question 14

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions are the making and breaking of chemical bonds.

Question 15

During photosynthesis, sunlight powers the conversion of carbon dioxide and water into glucose and oxygen. Which of the following correctly represents this process?

Accepted Answer

$$6\ \mathrm{CO}_2 + 6\ \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\ \mathrm{O}_2$$

Question 16

A chemical reaction has reached equilibrium when:

Accepted Answer

The forward and reverse reactions occur at the same rate.

Question 17

Which of the following best describes a trace element?

Accepted Answer

An element required by an organism in only minute quantities

Question 18

Which of the following is true about the atomic number and mass number of an element?

Accepted Answer

The atomic number is the number of protons, and the mass number is the sum of protons and neutrons.

Question 19

Which of the following best explains why elements with a full valence shell are chemically inert?

Accepted Answer

Their outermost electron shell is complete, so they do not tend to form chemical bonds.

Question 20

Which of the following is a real-world example of adaptation to toxic elements?

Accepted Answer

Some plant communities are adapted to serpentine soils containing toxic elements.

Atoms and Molecules: The Chemical Context of Life (Chapter 2 Study Notes)

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