Question 1

Which of the following statements best explains why isotopes of the same element have nearly identical chemical properties?

Accepted Answer

Because isotopes have the same number of protons and electrons, which determine chemical behavior.

Question 2

A neutral atom of magnesium (atomic number 12) has which of the following electron configurations?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$

Question 3

Which of the following best describes the process that occurs when sodium reacts with chlorine to form sodium chloride?

Accepted Answer

Sodium loses one electron to form $$Na^+$$, chlorine gains one electron to form $$Cl^-$$, and the resulting ions are held together by electrostatic attraction.

Question 4

Which of the following compounds is most likely to be a strong electrolyte in aqueous solution?

Accepted Answer

Sodium chloride ($$NaCl)$$

Question 5

A sample contains 36.03 grams of water ($$H_2O). $$What is the number of moles of water in the sample? (Molar mass of $$H_2O = 18.015\ g/mol)$$

Accepted Answer

$$2.0\ 	ext{mol}$$

Question 6

Which of the following best describes the role of a buffer solution in the human body?

Accepted Answer

It resists changes in pH when small amounts of acid or base are added.

Question 7

Which of the following is a correct balanced chemical equation for the complete combustion of propane ($$C_3H_8$$)?

Accepted Answer

$$C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O$$

Question 8

A solution is prepared by dissolving 0.2 moles of sodium chloride ($$NaCl) in $$enough water to make 500 mL of solution. What is the molarity ($$M) of $$the solution?

Accepted Answer

$$0.40\ M$$

Question 9

Which of the following statements about the structure of benzene ($$C_6H_6) is $$correct?

Accepted Answer

All carbon-carbon bonds in benzene are of equal length due to delocalized $$\pi$$ electrons.

Question 10

Which of the following best explains why phenol is more acidic than cyclohexanol?

Accepted Answer

The phenoxide ion formed after deprotonation is stabilized by resonance with the aromatic ring.

Question 11

A radioactive isotope has a half-life of 3 hours. If you start with 80 mg, how much remains after 9 hours?

Accepted Answer

$$10\ 	ext{mg}$$

Question 12

Which of the following best describes the difference between a saturated and an unsaturated fatty acid?

Accepted Answer

A saturated fatty acid contains only single bonds between carbon atoms, while an unsaturated fatty acid contains one or more double bonds.

Question 13

Which of the following is the correct IUPAC name for the compound with the structure $$CH_3CH_2CH_2OH$$?

Accepted Answer

Propan-1-ol

Question 14

Which of the following best describes the function of enzymes in biological systems?

Accepted Answer

They lower the activation energy of biochemical reactions, increasing the reaction rate.

Question 15

Which of the following is a correct statement about the law of definite proportions?

Accepted Answer

A given compound always contains the same elements in the same fixed ratio by mass.

Question 16

Which of the following best explains why transition metals often form colored compounds?

Accepted Answer

They have partially filled d-orbitals that allow electronic transitions absorbing visible light.

Question 17

A 250 mL sample of a 2.0 M $$NaOH$$ solution is diluted to a final volume of 1.0 L. What is the final concentration?

Accepted Answer

$$0.50\ M$$

Question 18

Which of the following best describes the Watson–Crick model of DNA structure?

Accepted Answer

DNA consists of two antiparallel strands forming a double helix, with complementary base pairing between adenine–thymine and guanine–cytosine.

Question 19

Which of the following is a correct statement about the acid–base properties of amino acids in aqueous solution?

Accepted Answer

Amino acids exist as zwitterions at their isoelectric point, with both a positive and a negative charge.

Question 20

Which of the following best explains why carboxylic acids have higher boiling points than alkanes of similar molecular mass?

Accepted Answer

Carboxylic acids form strong hydrogen bonds between molecules, increasing boiling point.

Comprehensive Study Notes for Introductory College Chemistry

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