Question 1

Which of the following statements best describes a compound?

Accepted Answer

A compound is a substance consisting of two or more elements in a fixed proportion.

Question 2

Which four elements make up approximately 96% of the human body’s weight?

Accepted Answer

Carbon, hydrogen, oxygen, nitrogen

Question 3

Why is iodine considered a trace element essential for human life?

Accepted Answer

It is a key component of hormones produced by the thyroid gland.

Question 4

Which of the following is NOT a trace element required by humans?

Accepted Answer

Oxygen

Question 5

If sodium (Na) and chlorine (Cl) combine to form sodium chloride (NaCl), which of the following best explains the change in properties?

Accepted Answer

The compound NaCl has entirely different properties than its constituent elements.

Question 6

Which statement about elements is correct?

Accepted Answer

Elements cannot be further broken down chemically.

Question 7

A patient is diagnosed with goiter, a swelling of the thyroid gland. Which dietary deficiency is most likely responsible?

Accepted Answer

Iodine

Question 8

Which of the following is a correct example of a compound?

Accepted Answer

H\_2O

Question 9

What is the main reason iron is considered an essential trace element?

Accepted Answer

It is a key component of hemoglobin, which is used to transport oxygen in blood.

Question 10

Which of the following best describes matter?

Accepted Answer

Matter always occupies space and has mass.

Question 11

A scientist discovers a new element in a living organism. Which property must this element have to be classified as an element?

Accepted Answer

It cannot be further broken down chemically.

Question 12

Which equation correctly represents the formation of sodium chloride from its elements?

Accepted Answer

$$\mathrm{Na} + \mathrm{Cl} \rightarrow \mathrm{NaCl}$$

Question 13

Which of the following elements is NOT one of the four main ingredients of sugars, fats, proteins, and nucleic acids?

Accepted Answer

Calcium

Question 14

Trace elements are required in which amounts for human life?

Accepted Answer

Very small amounts

Question 15

Which of the following is a correct statement about the chemical composition of living organisms?

Accepted Answer

All living things are composed of matter, which is made up of elements.

Question 16

Which element is a key component of table salt and is essential for nerve function?

Accepted Answer

Sodium

Question 17

A student claims that all elements are found in equal amounts in the human body. Which statement best refutes this claim?

Accepted Answer

Only four elements make up 96% of the human body’s weight.

Question 18

Which of the following is an example of a trace element that is essential for life but required in very small amounts?

Accepted Answer

Zinc

Question 19

Which of the following best explains why compounds are more common than free elements in nature?

Accepted Answer

Elements tend to combine to form compounds, which are more stable.

Basic Chemistry for Biology: Chemical Composition of Living Organisms

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