Q: Which of the following compounds is most likely to conduct electricity when dissolved in water?

Sodium chloride ($$\text{NaCl})$$

Q: A buffer solution is prepared using acetic acid ($$\text{CH}_3\text{COOH}) $$and sodium acetate ($$\text{CH}_3\text{COONa}). $$Which equation can be used to calculate the pH of this buffer?

$$\text{pH} = \text{p}K_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right)$$

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 patient is given a radioactive isotope for imaging. If the isotope has a half-life of 6 hours, what fraction of the original isotope remains after 18 hours?

Accepted Answer

$$\frac{1}{8}$$

Question 3

Which of the following best describes the electron configuration of a neutral magnesium atom (atomic number 12)?

Accepted Answer

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

Question 4

Which of the following compounds is most likely to conduct electricity when dissolved in water?

Accepted Answer

Sodium chloride ($$	ext{NaCl})$$

Question 5

A solution is prepared by dissolving 0.5 moles of sodium chloride in enough water to make 250 mL of solution. What is the molarity of the solution?

Accepted Answer

$$2.0\ 	ext{M}$$

Question 6

Which of the following best describes the law illustrated by the reaction: $$2	ext{H}_2 + 	ext{O}_2 ightarrow 2	ext{H}_2	ext{O}$$, where 8 g of hydrogen reacts with 64 g of oxygen to produce 72 g of water?

Accepted Answer

Law of Conservation of Mass

Question 7

Which of the following is a correct statement about the structure of benzene ($$	ext{C}_6	ext{H}_6$$)?

Accepted Answer

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

Question 8

A buffer solution is prepared using acetic acid ($$	ext{CH}_3	ext{COOH}) $$and sodium acetate ($$	ext{CH}_3	ext{COONa}). $$Which equation can be used to calculate the pH of this buffer?

Accepted Answer

$$	ext{pH} = 	ext{p}K_a + \log \left( \frac{[	ext{A}^-]}{[	ext{HA}]} ight)$$

Question 9

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

Accepted Answer

The phenoxide ion is stabilized by resonance delocalization over the aromatic ring.

Question 10

A 10.0 g sample of glucose ($$	ext{C}_6	ext{H}_{12}	ext{O}_6$$; molar mass = 180 g/mol) is dissolved in water to make 500 mL of solution. What is the molarity of the solution?

Accepted Answer

$$0.111\ 	ext{M}$$

Question 11

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

Accepted Answer

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

Question 12

Which of the following is a correct statement about the acid-base properties of amino acids in aqueous solution at physiological pH (about 7.4)?

Accepted Answer

Amino acids exist predominantly as zwitterions, with both a positive and a negative charge.

Question 13

Which of the following best explains why saturated fatty acids are solid at room temperature while unsaturated fatty acids are liquid?

Accepted Answer

Saturated fatty acids have straight chains that pack closely together, increasing van der Waals forces.

Question 14

A sample of potassium-40 ($$^{40}	ext{K}) $$has a half-life of 1.25 billion years. If a rock originally contained 8.0 mg of $$^{40}	ext{K}$$, how much remains after 3.75 billion years?

Accepted Answer

$$1.0\ 	ext{mg}$$

Question 15

Which of the following best describes the difference between a strong electrolyte and a weak electrolyte in aqueous solution?

Accepted Answer

A strong electrolyte completely dissociates into ions, while a weak electrolyte only partially dissociates.

Question 16

Which of the following is the correct IUPAC name for the compound with the structure $$	ext{CH}_3	ext{CH}_2	ext{CH}_2	ext{OH}$$?

Accepted Answer

Propan-1-ol

Question 17

Which of the following best describes the process of saponification?

Accepted Answer

The hydrolysis of triglycerides with a strong base to produce soap and glycerol.

Question 18

Which of the following statements about DNA structure is correct according to the Watson–Crick model?

Accepted Answer

Adenine pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds.

Question 19

A 0.200 M solution of hydrochloric acid ($$	ext{HCl}) is $$diluted to a final volume of 1.00 L. If the initial volume was 250 mL, what is the final concentration after dilution?

Accepted Answer

$$0.0500\ 	ext{M}$$

Comprehensive Study Notes for General Chemistry: Entrance Exam Topics

Guida di studio - Domande di pratica

Study guide - Flashcard