Question 1

Which subatomic particle is responsible for the atomic number of an element, and how is it calculated for phosphorus ($$^{31}P$$)?

Accepted Answer

Proton; calculated by counting the number of protons in the nucleus

Question 2

A solution has a pH of 4. Which of the following statements is correct regarding its acidity and hydrogen ion concentration?

Accepted Answer

It is acidic and has a high concentration of $$H^+$$ ions

Question 3

Which property of water allows it to moderate temperature changes in the environment, and what is the underlying molecular explanation?

Accepted Answer

High specific heat; hydrogen bonds absorb heat when they break and release heat when they form

Question 4

Which of the following best describes a buffer system in biological fluids?

Accepted Answer

A solution that resists significant changes in pH when small amounts of strong acids or bases are added

Question 5

Which type of bond involves the sharing of electrons between atoms, and is found in a water molecule ($$H_2O$$)?

Accepted Answer

Covalent bond

Question 6

A tracer is used in medical imaging to follow the path of a substance in the body. Which property makes a tracer effective for this purpose?

Accepted Answer

It is a radioactive isotope that emits detectable signals

Question 7

Which of the following substances is hydrophobic and why?

Accepted Answer

Olive oil; because it does not form hydrogen bonds with water

Question 8

If a molecule of ammonia ($$NH_3) is $$placed in water, what type of bond is most likely to form between ammonia and water molecules?

Accepted Answer

Hydrogen bond

Question 9

Which of the following best explains why ice floats on water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds keep water molecules farther apart in solid form

Question 10

A scientist wants to measure how difficult it is to stretch or break the surface of a liquid. Which property should they investigate?

Accepted Answer

Surface tension

Question 11

Which of the following best describes the difference between an isotope and a radioisotope?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons; radioisotopes are isotopes with unstable nuclei that emit energy

Question 12

Which of the following molecules is most likely to be hydrophilic?

Accepted Answer

Salt

Question 13

A solution is made by dissolving 10 g of NaCl in 100 mL of water. In this scenario, what is the solute?

Accepted Answer

NaCl

Question 14

Which of the following best describes the role of cohesion in the transport of water in plants?

Accepted Answer

Cohesion allows water molecules to stick together, enabling transport through xylem vessels

Question 15

Which of the following is true about the pH scale?

Accepted Answer

A solution with pH 7 is neutral

Question 16

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water is polar, allowing it to surround and separate positive and negative ions

Question 17

Which of the following best describes an ionic bond?

Accepted Answer

Electrons are transferred from one atom to another, resulting in oppositely charged ions

Question 18

A scientist adds a base to a solution, causing the pH to increase from 6 to 8. What does this change indicate about the concentration of $$H^+$$ ions?

Accepted Answer

The concentration of $$H^+$$ ions has decreased

Question 19

Which of the following best describes the difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons; nonpolar covalent bonds involve equal sharing

Atomic Structure, Chemical Bonds, and Properties of Water: Study Guide

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