【GR0627】 The Solution for GRE Chemistry Practice Test [01-20]

The Solution for GRE Chemistry Practice Test [01-20]

 

추천글 : 【GRE】 Solution for GRE Chemistry Practice Test 

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1. Of the following, which element has the highest first ionization energy? 

 

 

⑴ answer: A

⑵ first ionization energy : Rb ＜ Sr ＜ Ga ＜ Ge ＜ As

 

 

 

2. Which of the following is the most acceptable Lewis electron dot structure for carbon monoxide? 

 

 

⑴ answer: C

⑵ Lewis electron dot structure determination

⑶ step 1. C:: :::O

⑷ step 2. :C=O:: → Not probable because octat rule is not established.

⑸ step 3. :C≡O: → 🄒

⑹ step 4. C≣O: → Not probable because octat rule is not established.

 

 

3. What is the correct IUPAC name for the compound shown below?

 

 

⑴ answer: C

⑵ step 1. E isomer (ref.)

⑶ step 2. main chain : 5 carbones. -pen-

⑷ step 3. functional group : alkene. -ene

⑸ step 4. numbering : The lower the alkene number, the more prioritized. Here, the alkene number is 2.

⑹ step 5. substituent : 3-methyl-

⑺ final nomenclature : (E)-3-methyl-2-pentene

 

 

4. What is the total number of stereoisomers possible for the compound shown below?

 

 

⑴ answer: D

⑵ Three chiral centers (i.e., carbons connected to -Cl or -OH) are distinct, so the number is 2³ = 8.

 

 

5. The total number of peptide bonds in the structure shown below is 

 

 

⑴ answer: C

⑵ # of peptide bonds = # of -CONH-

 

 

6. A 0.10 L solution of Cl^- (aq) is titrated with 1.0 × 10^-3 M Ag⁺ (aq). The end point is reached when 0.025 L of the Ag⁺ solution has been added. What was the concentration of Cl^- in the original solution?

 

 

⑴ answer: B

⑵ x × 0.10 = 0.001 × 0.025 → x = 2.5 × 10^-4 M

 

 

7. ΔH for the reaction shown below is greater than zero. Assuming ΔH is independent of temperature, which of the following statements about the percent yield of CO (g) is true? 

 

 

⑴ answer: B

⑵ principle of Le Chatelier : As the temperature of the system increases, the endothermic reaction prevails.

 

 

8. The initial rates given below were determined for the reaction A + 2B → AB₂. What is the overall rate low for this reaction?

 

 

⑴ answer: D

⑵ 1st experiment ↔ 2nd experiment : rate ∝ [B]

⑶ 1st experiment ↔ 3rd experiment : rate ∝ [A]

⑷ ∴ rate = k[A][B]

 

 

9. Assuming that air is approximately 80 percent nitrogen and 20 percent oxygen by volume, which of the following is closest to the density of air at 0 ℃ and 1 atmosphere?

 

 

⑴ answer: C

⑵ At 0 ℃ and 1 atmosphere, the volume of 1 mol air is 22.4 L. 

⑶ As the number of air particles is proportional to the volume percent, there are 80 % nitrogen and 20 % oxygen by number. 

⑷ ∴ ρ = (0.8 mol × 28 g N₂/mol + 0.2 mol × 32 g O₂/mol) ÷ 22.4 L = 1.285714 g/L

 

 

10. How many π bonds are there in acetylene, shown below?

 

 

⑴ answer: B

 

 

 

11. In which of the following are the carboxylic acids shown below listed in order of decreasing acidity, from most acidic to least acidic?

 

 

⑴ answer: C

⑵ inductive effect : σ bonding of electronegative atoms (e.g., F) increases acidity by withdrawing electrons.

 

 

12. Which of the following is a 1,4-additional product of the reaction shown below? 

 

 

⑴ answer: C

⑵ hydrogen halide addition to alkene 

 

 

 

13. Which of the following is a weak Brønsted–Lowry acid?

 

 

⑴ answer: D

⑵ acid : H⁺ donor 

⑶ base : H⁺ acceptor 

 

 

14. Which of the following correctly lists the species in order of increasing radius from smallest to largest? 

 

 

⑴ answer: A

⑵ When the number of electrons is the same, the radius decreases as the atomic number increases.

 

 

15. The half-life of ¹⁴C is 5,730 years. All of the following are true for the method of carbon dating EXCEPT:

 

 

⑴ answer: E

⑵ β-decay

 

 

⑶ Samples that are millions of years old are too long to use carbon dating accurately.

 

 

16. The curve shown below illustrates the Pv̅ behavior of a real gas, where v̅ is the molar volume. According to the van der Waals model for nonideal gas behavior, the values of Pv̅ / RT greater than 1.0 at high pressures are due to  

 

 

⑴ answer: C

⑵ van der Waals model

 

 

⑶ high pressure : The repulsive force by molecular interactions can be neglected.

⑷ high pressure : Rather, the volume occupied by the molecules should be considered due to the small total volume.

 

 

17. For the reaction shown below at 298 K, ΔGº = -163 kJ/mol. What is the value of the equilibrium constant, K_p, for this reaction?

 

 

⑴ answer: A

⑵ ΔG = ΔGº + RT ln K_p = 0 ⇔ ΔGº = - RT ln K_p ＜ 0

⑶ ∴ K_p ＞ 1.0

 

 

18. In an isolated hydrogen atom, the 2p_x orbital has the same principal quantum number, n, as which of the following orbitals? 

 

 

⑴ answer: D

 

 

19. Which of the following is NOT an allotrope of carbon?

 

 

⑴ answer: E

 

 

20. Of the following covalent bonds, which has the greatest bond dissociation energy?

 

 

⑴ answer: E

⑵ Dissociation energy increases as the bond order increases, the atomic radius decreases, or the polarity (ΔEN) increases.

 

입력: 2023.06.05 01:38