Q: Which of the following equations correctly represents how to calculate the mass number of an atom?

$$\text{Mass number} = \text{number of protons} + \text{number of neutrons}$$

Question 1

Which of the following best describes a trace element, and why are trace elements important for living organisms?

Accepted Answer

A trace element is a small amount of an element found in the body that is necessary for vital biological functions, such as iron or zinc.

Question 2

Which of the following equations correctly represents how to calculate the mass number of an atom?

Accepted Answer

$$	ext{Mass number} = 	ext{number of protons} + 	ext{number of neutrons}$$

Question 3

A radioactive isotope of carbon, $$^{14}	ext{C}$$, is used to date ancient fossils. What property of $$^{14}	ext{C}$$ makes it useful for this purpose?

Accepted Answer

It emits radiation at a constant rate, allowing scientists to estimate the age of fossils based on the remaining amount.

Question 4

Which of the following best explains why water molecules are cohesive?

Accepted Answer

Water molecules are cohesive due to hydrogen bonding between the slightly positive hydrogen atom of one molecule and the slightly negative oxygen atom of another.

Question 5

A solution has a pH of 9. How many times more basic is this solution compared to a solution with a pH of 7?

Accepted Answer

$$100$$ times more basic

Question 6

Which of the following statements about covalent and ionic bonds is correct?

Accepted Answer

Covalent bonds are generally stronger than ionic bonds and involve the sharing of electron pairs between atoms.

Question 7

Which of the following best describes the process of ocean acidification?

Accepted Answer

CO$$_2$$ from the atmosphere dissolves into the ocean, lowering the pH and making the water more acidic, which interferes with the formation of coral skeletons.

Question 8

If an atom has an atomic number of 8 and a mass number of 18, how many neutrons does it have?

Accepted Answer

$$10$$ neutrons

Question 9

Which of the following is a correct definition of a base in terms of pH and hydrogen ion concentration?

Accepted Answer

A base is a substance that reduces the hydrogen ion concentration of a solution, resulting in a higher pH.

Question 10

Which of the following best describes the difference between a solute and a solvent in a solution?

Accepted Answer

The solute is the substance being dissolved, and the solvent is the substance that does the dissolving.

Question 11

A scientist is studying a molecule that has a partial positive charge on one end and a partial negative charge on the other. What type of molecule is this, and what property does it exhibit?

Accepted Answer

It is a polar molecule and exhibits the ability to form hydrogen bonds.

Question 12

Which of the following best explains why surface tension occurs in water?

Accepted Answer

Surface tension occurs because of the strong hydrogen bonds between water molecules at the surface, making it difficult to break through the surface.

Question 13

Which of the following is the correct formula for calculating the pH of a solution?

Accepted Answer

$$	ext{pH} = -\log_{10} [	ext{H}^+]$$

Question 14

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 15

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-5}$$ M. What is the pH of this solution?

Accepted Answer

$$5$$

Question 16

Which of the following best describes the effect of burning fossil fuels on coral reefs?

Accepted Answer

Burning fossil fuels releases CO$$_2$$, which dissolves in ocean water, lowers the pH, and makes it harder for corals to form calcium carbonate skeletons.

Question 17

Which of the following is a property of acids in aqueous solutions?

Accepted Answer

Acids donate H$$^+$$ ions to solution, increasing the concentration of H$$^+.$$

Question 18

Which of the following best describes a hydrogen bond?

Accepted Answer

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

Question 19

Which of the following is true about the relationship between atomic number and the number of protons in an atom?

Accepted Answer

The atomic number is equal to the number of protons in the atom.

Question 20

Which of the following best explains why ionic bonds are generally weaker in aqueous (water-based) solutions than in dry conditions?

Accepted Answer

Water molecules surround and shield the ions, reducing the electrostatic attraction between them.

General Biology: Elements, Chemical Bonds, Water Properties, and pH

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