Q: A solution has a pH of 4. What is the hydrogen ion concentration $$[\mathrm{H}^+] in $$this solution?

$$1 \times 10$$^{-4}$$\ \mathrm{M}$$

Question 1

Which four elements make up approximately 96% of living matter in organisms?

Accepted Answer

Oxygen, carbon, hydrogen, nitrogen

Question 2

According to the octet rule, how many electrons does an oxygen atom need to gain to achieve a stable configuration?

Accepted Answer

2

Question 3

What type of chemical bond is formed when sodium (Na) transfers an electron to chlorine (Cl)?

Accepted Answer

Ionic bond

Question 4

Which property of water allows it to absorb or release a large amount of heat with only a slight change in temperature?

Accepted Answer

High specific heat

Question 5

Why is ice less dense than liquid water?

Accepted Answer

Hydrogen bonds keep water molecules farther apart in ice

Question 6

Which equation correctly expresses the relationship between pH and hydrogen ion concentration?

Accepted Answer

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

Question 7

A solution has a pH of 4. What is the hydrogen ion concentration $$[\mathrm{H}^+] in $$this solution?

Accepted Answer

$$1 	imes 10$$^{-4}$$\ \mathrm{M}$$

Question 8

Which of the following best explains why water is a versatile solvent?

Accepted Answer

Its polarity allows it to form hydration shells around ions and polar molecules

Question 9

What is the main function of buffers in biological systems?

Accepted Answer

To minimize changes in pH by accepting or donating hydrogen ions

Question 10

Which type of chemical bond involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 11

Which property of water is most responsible for the movement of water up plant stems against gravity?

Accepted Answer

Cohesion and adhesion

Question 12

If the concentration of $$[\mathrm{H}^+] in a $$solution is $$1 	imes 10$$^{-7}$$\ \mathrm{M}$$, what is the pH of the solution?

Accepted Answer

7

Question 13

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

Accepted Answer

Iron (Fe)

Question 14

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally between two atoms

Question 15

What is the result when a sodium atom loses an electron?

Accepted Answer

It becomes a positively charged ion ($$\mathrm{Na}^+)$$

Question 16

Which property of water allows sweating to cool the body?

Accepted Answer

High heat of vaporization

Question 17

Which of the following is the weakest type of intermolecular attraction?

Accepted Answer

Van der Waals interaction

Question 18

A buffer system in blood involves carbonic acid ($$\mathrm{H}_2\mathrm{CO}_3) $$and bicarbonate ($$\mathrm{HCO}_3^-). $$What happens when blood becomes too acidic?

Accepted Answer

Bicarbonate ions combine with excess $$\mathrm{H}^+ to $$form carbonic acid

Question 19

Which of the following best explains why nonpolar molecules do not dissolve well in water?

Accepted Answer

They lack charged or polar regions to interact with water's polarity

Question 20

If a solution has a pH of 2 and another has a pH of 4, how many times more acidic is the pH 2 solution compared to the pH 4 solution?

Accepted Answer

100 times

The Chemistry of Life: Elements, Bonds, Water, and Acids/Bases

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