Q: Which equation correctly represents the photosynthesis reaction described in the study materials?

$$6CO_2 + 6H_2O \xrightarrow{\text{sunlight}} C_6H_{12}O_6$ + 6O_2$$

Question 1

Which of the following statements best explains why compounds have characteristics different from those of their constituent elements?

Accepted Answer

Compounds are formed by chemical bonding between elements in fixed ratios, resulting in new emergent properties.

Question 2

A radioactive isotope of carbon, carbon-14, is commonly used in dating fossils. What property of carbon-14 makes it useful for this purpose?

Accepted Answer

It decays spontaneously at a predictable rate, allowing measurement of elapsed time.

Question 3

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

Accepted Answer

A molecule consists of two or more atoms held together by covalent bonds, while a compound consists of two or more different elements in a fixed ratio.

Question 4

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 5

An atom of sodium (Na) has 11 protons and 12 neutrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: 11, Mass number: 23

Question 6

Which of the following elements is NOT one of the four that make up 96% of living matter?

Accepted Answer

Phosphorus

Question 7

What is the main reason noble gases such as helium and neon are chemically inert?

Accepted Answer

They have full valence electron shells.

Question 8

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the attraction between oppositely charged ions after electron transfer.

Question 9

Which equation correctly represents the photosynthesis reaction described in the study materials?

Accepted Answer

$$6CO_2 + 6H_2O \xrightarrow{	ext{sunlight}} C_6H_{12}O_6$ + 6O_2$$

Question 10

Which of the following is a trace element required by living organisms in minute quantities?

Accepted Answer

Iron

Question 11

A patient is injected with a radioactive isotope to trace a metabolic pathway. Which property of the isotope is most important for this application?

Accepted Answer

It emits detectable particles or energy as it decays.

Question 12

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 13

Which of the following is true about van der Waals interactions?

Accepted Answer

They result from temporary 'hot spots' of charge in molecules.

Question 14

If an atom has 8 protons, 8 neutrons, and 8 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number: 8, Mass number: 16

Question 15

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons and has a positive charge.

Question 16

Which of the following is the correct formula for calculating the mass number of an atom?

Accepted Answer

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

Question 17

Which of the following best describes a chemical reaction?

Accepted Answer

A process that makes and breaks chemical bonds, resulting in new substances.

Question 18

Which of the following statements about covalent bonds is correct?

Accepted Answer

A double covalent bond involves sharing two pairs of electrons.

Question 19

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

Accepted Answer

Using iodine-131 to diagnose thyroid disorders.

Question 20

Which of the following best explains why weak chemical bonds are important in biological systems?

Accepted Answer

They reinforce shapes of large molecules and help molecules adhere to each other.

Chemical Context of Life: Atoms, Elements, and Chemical Bonds

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