【GR1727】 The Solution for GRE Chemistry Practice Test [61-80]

The Solution for GRE Chemistry Practice Test [61-80] 

 

추천글 : 【GRE】 Solution for GRE Chemistry Practice Test 

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61. Which of the following is the major product of the reaction shown below?

 

 

⑴ answer: C

⑵ alkene epoxidation 

 

 

62. What is the product of the reaction shown below? 

 

 

⑴ answer: E

⑵ addition of amine to acyl chloride 

 

 

63. Which of the following procedures tend(s) to minimize the influence of random errors on measured results?

Ⅰ. Signal averaging

Ⅱ. Use of internal standards

Ⅲ. Averaging the results from multiple samples

 

 

⑴ answer: D

 

 

64. A buffer is made of from equal concentrations of a weak acid and its conjugate base. Doubling the volume of the buffer solution by adding water has what effect on its pH?

 

 

⑴ answer: A

⑵ Henderson-Hasselbalch equation 

 

 

65. Which of the following is the most common naturally-occurring from in which silicon is found?

 

 

⑴ answer: D

⑵ Because of the abundance of oxygen in nature.

 

 

66. A substance that is NOT generally considered to be a toxic pollutant in water is 

 

 

⑴ answer: A

⑵ For example, sea water has a lot of carbonic acid.

 

 

67. Which of the following is an n-type semiconductor? 

 

 

⑴ answer: D

⑵ p-type (positive-type semiconductor) and n-type (negative-type semiconductor)

 

 

68. Which of the following is lower for argon than for neon?

 

 

⑴ answer: E

⑵ Ionization energy decreases as the number of electron shells increases.

 

 

69. For EDTA titrations, the analyte solution and the titrant solution are both buffered at the same pH for which of the following reasons?

Ⅰ. The conditional formation constant is affected by pH. 

Ⅱ. The fraction of EDTA in the fully deprotonated Y^4- form varies with pH. 

Ⅲ. When EDTA reacts to form a metal complex, H⁺ is a product in most cases. 

 

 

⑴ answer: E

⑵ Experimentally, the strength of the coordinate covalent bond differs according to pH.

 

 

70. The Henry's law constant for CO₂ dissolved in water at 25 ℃ is 30.0 atm M^-1. The concentration of dissolved CO₂ in a vessel pressurized with 2.0 atm of CO₂ is 

 

 

⑴ answer: C

⑵ x M × 30.0 atm M^-1 = 2.0 atm → x = 2 / 30 = 0.067 

 

 

71. The gas-phase reaction A → product is postulated to proceed by the mechanism shown below, in which A* is an activated A molecule and M is a chemically inert gas.

 

 

Assuming the steady-state approximation for A*, this mechanism yields the rate equation like below.

 

 

Which of the following is NOT consistent with the mechanism?

 

 

⑴ answer: D

⑵ When the partial pressure of M is very low, the rate is close to 0. 

 

 

72. System A and system B above are identical closed systems that undergo a change of state from the same initial conditions (P₁, V₁, T₁) to the same final conditoins (P₂, V₂, T₂), but by a different process. What are ΔU and q for the change in state for system B?

 

 

⑴ answer: B

⑵ ΔU (B) = ΔU (A) = q (A) + w (A) = 0 - 300 = -300 (J)

⑶ q (B) = ΔU (B) - w (B) = -300 - (-200) = -100 (J)

 

 

73. Chlorofluorocarbons (CFCs) such as F₃CCCl₃ are implicated in the decomposition of stratospheric ozone. Which of the following methods would be best suited to measurement of trace amounts (sub-ppb) of CFCs in an air sample? 

 

 

⑴ answer: A 

 

 

74. Which of the following best depicts the initial nucleophilic addition step in the acid-catalyzed hydrolysis of acetonitrile shown below?

 

 

⑴ answer: B

⑵ acid-catalyzed nitrile hydration reaction 

 

 

75. Which of the following is the hemiacetal intermediate in the reaction shown below?

 

 

⑴ answer: C

 

 

76. What is the major product of an E2 reaction of the compound shown below? 

 

 

⑴ answer: A

⑵ Anti-periplanar rule should be considered in the E2 reaction of cyclic compounds.

 

 

77. Of the following fatty acids, which has the lowest melting point? 

 

 

⑴ answer: E

⑵ It is well-known that unsaturated lipids have lower melting points due to the lack of intermolecular crystality.

 

 

78. Of the following compounds, which is LEAST likely to behave as a Lewis acid?

 

 

⑴ answer: D

⑵ Only SCl₂ among them lacks the metal species.

 

 

79. The strongest base in liquid ammonia is 

 

 

⑴ answer: B

⑵ The more negative charge, the more strong in basicity.

 

 

80. Which of the following lists the hydrides of group-14 elements in order of thermal stability, from lowest to highest? 

 

 

⑴ answer: A

⑵ The central element with higher size is disadvantageous in orbital overlapping with hydrogen, thus unstable thermally.

 

입력: 2022.03.04 09:51