Q: If a solution has $$[OH^-] = 1 \times 10$$^{-6}$$ M, what is its pH?

$$pOH = -\log_{10}(1 \times 10$$^{-6}$$) = 6$$, so $$pH = 14 - 6 = 8$$

Question 1

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

Accepted Answer

The oxygen atom in water attracts shared electrons more strongly than hydrogen, resulting in partial charges.

Question 2

A radioactive isotope of carbon has a half-life of 2 hours. If you start with 80 grams, how much will remain after 6 hours?

Accepted Answer

$$80 \div 2^3$ = 10$$ grams

Question 3

Which property of water is most directly responsible for the ability of some insects to walk on water?

Accepted Answer

Cohesion due to hydrogen bonding

Question 4

What is the molarity of a solution made by dissolving 29 grams of NaCl (molecular mass = 58 g/mol) in 1 liter of water?

Accepted Answer

$$M = \frac{29}{58} = 0.5 M$$

Question 5

Which statement best describes the difference between covalent and ionic bonds?

Accepted Answer

Covalent bonds involve the sharing of electron pairs, while ionic bonds involve the transfer of electrons resulting in charged ions.

Question 6

A solution has $$[H^+] = 0.001 M. $$What is its pH?

Accepted Answer

$$pH = -\log_{10}(0.001) = 3$$

Question 7

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

Accepted Answer

Magnesium

Question 8

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice form a crystalline lattice that spaces molecules farther apart, making ice less dense.

Question 9

Which of the following best describes a buffer in biological systems?

Accepted Answer

A buffer is a substance that minimizes changes in pH by accepting or donating $$H^+$$ ions.

Question 10

Which emergent property of water helps stabilize climate and organism temperature?

Accepted Answer

High specific heat

Question 11

If a solution has $$[OH^-] = 1 	imes 10$$^{-6}$$ M, what is its pH?

Accepted Answer

$$pOH = -\log_{10}(1 	imes 10$$^{-6}$$) = 6$$, so $$pH = 14 - 6 = 8$$

Question 12

Which of the following is NOT a consequence of water’s hydrogen bonding?

Accepted Answer

Water’s nonpolar nature

Question 13

Which type of chemical bond is primarily responsible for the formation of table salt (NaCl)?

Accepted Answer

Ionic bond

Question 14

A scientist wants to make a 2 M solution of glucose ($$C_6H_{12}O_6$, molecular mass = 180 g/mol) in 1 liter of water. How many grams of glucose are needed?

Accepted Answer

$$2 	imes 180 = 360$$ grams

Question 15

Which of the following best describes electronegativity?

Accepted Answer

The ability of an atom to attract shared electrons in a covalent bond.

Question 16

Which of the following statements about acids and bases is correct?

Accepted Answer

Acids increase the $$H^+$$ concentration in a solution.

Question 17

Which property of water is most important for the transport of water from roots to leaves in plants?

Accepted Answer

Cohesion and adhesion

Question 18

What is the main reason ionic compounds like NaCl dissolve easily in water?

Accepted Answer

Water molecules surround ions, forming hydration shells due to water’s polarity.

Question 19

Which of the following is a correct statement about chemical equilibrium?

Accepted Answer

At equilibrium, the forward and reverse reaction rates are equal.

Question 20

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

Accepted Answer

Medical diagnostics and radiometric dating

Fundamental Chemical Principles and Water in Biology

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