Question 1

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

Accepted Answer

They have a full valence shell of electrons, satisfying the octet rule.

Question 2

A neutral 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 3

Which property of water allows insects to walk on its surface?

Accepted Answer

Cohesion due to hydrogen bonding

Question 4

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the transfer of electrons from one atom to another, resulting in oppositely charged ions

Question 5

Given the molecular formula $$\mathrm{C_6H_{12}O_6$}$$, how many atoms are present in one molecule of glucose?

Accepted Answer

$$6 + 12 + 6 = 24$$ atoms

Question 6

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 7

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice form a rigid, open structure that is less dense than liquid water.

Question 8

A solution has a pH of 4. What is the hydrogen ion concentration compared to a solution with a pH of 6?

Accepted Answer

It is 100 times greater.

Question 9

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

Accepted Answer

Buffers help maintain a stable pH by absorbing or releasing hydrogen ions as needed.

Question 10

Which of the following is a real-life application of radioactive isotopes in medicine?

Accepted Answer

Using I-131 as a tracer for thyroid scans

Question 11

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 surround and separate ions and polar molecules.

Question 12

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally, resulting in partial charges on the atoms.

Question 13

If a neutral atom has 17 protons, 18 neutrons, and 17 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number = 17, Mass number = $$17 + 18 = 35$$

Question 14

Which property of water is most important for maintaining a stable internal temperature in living organisms?

Accepted Answer

High heat capacity

Question 15

Which of the following best describes the octet rule?

Accepted Answer

Atoms are most stable when their outermost shell contains eight electrons.

Question 16

Which of the following is a consequence if the ice on lakes and oceans did not float?

Accepted Answer

Bodies of water would freeze solid from the bottom up, threatening aquatic life.

Question 17

Which of the following best explains why sodium (Na) and chlorine (Cl) form an ionic bond?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 18

A buffer system in human blood involves carbonic acid ($$\mathrm{H_2CO_3}) $$and bicarbonate ($$\mathrm{$$HCO_3$$^-}). $$What happens if a small amount of acid is added to the blood?

Accepted Answer

The buffer will absorb the excess $$\mathrm{H^+}$$ ions, minimizing the change in pH.

Question 19

Which of the following is a direct result of water's polarity?

Accepted Answer

Water can dissolve ionic and polar substances.

Question 20

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule consists of two or more atoms bonded together, while a compound consists of two or more different elements bonded together.

Fundamental Chemistry Concepts for Nutrition Students

Guida di studio - Domande di pratica

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