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• Question 131:

  What would be the percentage mass of chlorine in a molecule of methyl chloride? (C = 12 gm/mole, H = 1 gm/mole, Cl = 35.5 gm/mole).

  A. 18 %

  B. 50 %

  C. 70 %

  D. 12 %

  Correct Answer: C

  The molecular formula for methyl chloride is CH3Cl. The mass of a chlorine atom in methyl chloride is 35.5 gm/mole. The molecular weight of methyl chloride is 50.5 gm/mole (1C = 12, 3H = 3 and 1Cl = 35.5). Therefore, the % mass of chlorine in methyl chloride will be 35.5 / 50.5 = 70%

• Question 132:

  The region in space where an electron is likely to be found is called a(n):

  A. Axis

  B. Cloud

  C. Orbital D. Configuration

  Correct Answer: C

  The region in space where an electron is likely to be found is called an orbital. There are different kinds of orbitals with different sizes and shapes. The orbital at the lowest energy level is defined as a 1s orbital. It is a sphere with its center at the nucleus of the atom. The next higher energy level is called a 2s orbital. It is larger than a 1s orbital. Since it has a higher energy level, it has lower stability compared to a 1s orbital. This is because the average distance between the nucleus and electrons in a 2s orbital is greater than in a 1s orbital. The next three orbitals are of equal energy, known as 2p orbitals. They are dumbbell-shaped. They are further differentiated by the names 2px, 2py, and 2pz, where the x, y, and z refer to the corresponding axes.

• Question 133:

  The rate law for a reaction is of the second order. Which statement is true?

  A. The rate must depend on both reactants.

  B. The reaction must depend on the square of one reactant.

  C. The reaction must depend on only k squared.

  D. The reaction must depend on at least one of the reactants.

  Correct Answer: D

  In a second-order reaction the reaction rate is dependent upon either the product of the reactants, or the square of one of the reactants.

• Question 134:

  Which of the following has the highest boiling point?

  A. methanol

  B. n-propanol

  C. isopropanol

  D. ethanol

  Correct Answer: B

  Boiling points primarily depend upon the cohesive forces between molecules. When dealing with molecules of relatively similar molecular weights, the boiling points will depend upon the functional groups involved, and as the molecular weight of the molecule increases, the boiling point also increases. Lastly, branching decreases boiling point. With these considerations, n-propanol will exhibit the highest boiling point of the options.

• Question 135:

  What is the result of adding HBr and hydrogen peroxide to propene?

  A. 2-propanol

  B. 1-propanol

  C. 2-bromopropane

  D. 1-bromopropane

  Correct Answer: D

  In the presence of an organic peroxide, the addition of HBr (and peroxide) to a propene results in an anti-Markovnikov product in which the hydrogen becomes attached to the carbon with fewer hydrogens connected to it. The product of the addition is CH3CH2CH2Br, or 1-bromopropane.

• Question 136:

  Rank the following amino acids by increasing pI (isoelectric point):

  I. Lys

  II. Leu

  III.

  Asp

  A.

  I < II < III

  B.

  III < II < I

  C.

  II < I < III

  D.

  III < I < II

  Correct Answer: B

  The pI of a molecule is its isoelectric point, or the point at which, in this case, the amino acid will have no overall charge. Categorizing the amino acids: (I) is positively charged and basic; (II) is non polar and neutral; (III) is polar and acidic. Acidic amino acids on average have the lowest pI, nonpolar amino acids have a higher pI, and basic amino acids carry the largest pI.

• Question 137:

  Which effect would result from increasing the molar mass of a gas?

  A. An increase in temperature

  B. An increase on pressure

  C. An increase in volume

  D. A decrease in the rate

  Correct Answer: D

  Graham's Law of Diffusion states that the rate of diffusion is inversely proportional to the molecular weight of the molecule. Let the initial molar mass be 5, and the increased molar mass be 10, substitute these values into Graham's equation and compare the results:

  

  The rate has decreased with the increase in molar mass.

• Question 138:

  Which of the following species cannot hydrogen bond with itself?

  A. ethanol

  B. acetic acid

  C. ammonia

  D. acetone

  Correct Answer: D

  Hydrogen bonds occur between hydrogen of one molecule with an electronegative atom (oxygen, nitrogen, or fluorine) of another atom. Consequently, acetone is unable to hydrogen bond with itself. The hydrogen atoms in acetone are covalently bonded to carbon atoms and not a strong electronegative atom like nitrogen, oxygen, of fluorine.

• Question 139:

  What is the conjugate base of sulfuric acid?

  

  A. Option A

  B. Option B

  C. Option C

  D. Option D

  Correct Answer: B

• Question 140:

  What would be the result of increasing the number of nucleophiles in a SN1 reaction?

  A. It would increase the rate exponentially.

  B. It would increase the rate linearly.

  C. It would decrease the rate.

  D. It would have no effect.

  Correct Answer: D

  SN1 reactions are substitution reactions that depend on reagents attracted to electrons (electrophiles).

  SN1 reactions do not depend on the number of nucleophiles involved in the reaction. Consequently, altering the concentration of nucleophiles does not alter the rate of reaction.