Part II. Multiple choice, continued (3 points each). Name:__________________ Please circle your answer. There is only one correct answer to each question. 27. What volume (mL) of 0.135 M NaOH is required to neutralize 13.7 mL of 0.129 M HCl? A) 13.1 B) 0.24 C) 14.3 D) 6.55 28. All of the orbitals in a given electron shell have the same value of the ___________ quantum number. A) principal B) azimuthal C) magnetic D) spin 29. The places where the value of Y2 is zero are called ___________. A) orbitals B) nodes C) orbits D) wave functions 30. Of the following elements, which has the largest first ionization energy? A) B B) N C) P D) Si 31. Which equation correctly represents the second ionization of phosphorous? A) P+(g) + e- à P2+(g) B) P(g) à P+(g) + e- C) P+(g) à P2+(g) + e- D) P-(g) + e- à P2-(g) 32. Which of the following does not have eight valence electrons? A) Rb+ B) Ca+ C) Xe D) Br- 33. Of the atoms below, ____________ is the least electronegative. A) Cl B) Si C) F D) Rb 34. Of the bonds below, __________ is the least polar. A) Na - S B) P - S C) Na - Cl D) Si - Cl 35. In the Lewis structure of ClF, the formal charge on Cl is ______ and the formal charge on F is ________. A) –1, -1 B) 0, -1 C) 0, 0 D) +1, -1

Here's an in-depth explanation of the concepts covered in the multiple-choice questions:

27. Neutralization Reaction

    • The key to solving this problem is the concept of stoichiometry and the balanced chemical equation for the neutralization reaction between NaOH and HCl:
      \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}
    • From the balanced equation, the mole ratio between NaOH and HCl is 1:1. Therefore, at the equivalence point (neutralization), the number of moles of NaOH will equal the number of moles of HCl.
    • Moles of HCl can be calculated using the formula: \text{moles} = \text{Molarity} \times \text{Volume (in L)}
      \text{moles of HCl} = 0.129 \,\text{M} \times 0.0137 \,\text{L} = 0.0017673 \,\text{moles}
    • Since moles of NaOH = moles of HCl at neutralization:
      \text{Volume of NaOH} = \frac{\text{moles}}{\text{Molarity}} = \frac{0.0017673 \,\text{moles}}{0.135 \,\text{M}} = 0.0131 \,\text{L}
    • Convert liters to milliliters: 0.0131 \,\text{L} \times 1000 = 13.1 \,\text{mL}
    • Correct Answer: A) 13.1

28. Quantum Numbers

    • Principal Quantum Number (n): Determines the energy level or electron shell of an electron. It can be any positive integer (n = 1, 2, 3, …). All orbitals within the same electron shell have the same principal quantum number.
    • Azimuthal Quantum Number (l): Determines the shape of the orbital and has values ranging from 0 to n-1. (l = 0, 1, 2, …, n-1). These values correspond to s, p, d, and f orbitals, respectively.
    • Magnetic Quantum Number (ml): Determines the orientation of the orbital in space. It can take integer values from -l to +l, including 0.
    • Spin Quantum Number (ms): Determines the spin of the electron, which can be either +1/2 or -1/2.
    • Correct Answer: A) principal

29. Nodes

    • In quantum mechanics, a node is a point where the wave function (Ψ) of an electron has a value of zero. Since Ψ^2 represents the probability density of finding an electron at a particular point, a node is a place where there is zero probability of finding the electron.
    • Correct Answer: B) nodes

30. Ionization Energy

    • Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The first ionization energy is the energy required to remove the first electron.
    • Trends in ionization energy: Ionization energy generally increases across a period (from left to right) and decreases down a group (from top to bottom).
    • Nitrogen has a higher first ionization energy than expected because of its electron configuration. Nitrogen has a half-filled p subshell, which is particularly stable.
    • Correct Answer: B) N

31. Second Ionization

    • The second ionization energy is the energy required to remove a second electron from an ion. This always requires more energy than the first ionization because you are removing an electron from a positively charged ion.
    • The general form for the second ionization of an element X is:
      X^+(g) \rightarrow X^{2+}(g) + e^-
    • Correct Answer: C) P+(g) à P2+(g) + e-

32. Valence Electrons

    • Valence electrons are the electrons in the outermost shell of an atom. Atoms gain, lose, or share valence electrons to achieve a stable electron configuration, usually with eight valence electrons (the octet rule).
    • Rb+: Rubidium (Rb) is in Group 1. Rb+ has lost its one valence electron and now has the same electron configuration as Krypton (Kr), which has eight valence electrons in its outermost shell.
    • Ca+: Calcium (Ca) is in Group 2. Ca+ has lost one of its two valence electrons. Its electron configuration is not noble gas configuration and does not have eight valence electrons (it has the same electron configuration as potassium).
    • Xe: Xenon (Xe) is a noble gas and has eight valence electrons.
    • Br-: Bromine (Br) is in Group 17. Br- has gained one electron to have eight valence electrons and achieve the electron configuration of Krypton (Kr).
    • Correct Answer: B) Ca+

33. Electronegativity

    • Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons towards itself.
    • Trends in electronegativity: Electronegativity generally increases across a period (from left to right) and decreases down a group (from top to bottom).
    • Rubidium (Rb) is in Group 1 and is located far to the left and down the periodic table compared to the other options, making it the least electronegative.
    • Correct Answer: D) Rb

34. Bond Polarity

    • Bond polarity depends on the difference in electronegativity between the two atoms in the bond. The greater the difference in electronegativity, the more polar the bond.
    • Smallest difference indicates the least polar bond. From the electronegativity trends: Electronegativity of P is approximately equal to S, therefore, the difference will be the smallest.
    • Correct Answer: B) P - S

35. Formal Charge

    • Formal charge is the charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity.
    • Formal Charge = (Valence electrons) - (Non-bonding electrons) - (1/2 Bonding electrons)
    • For ClF, Chlorine (Cl) has 7 valence electrons, and Fluorine (F) also has 7 valence electrons. The Lewis structure of ClF involves a single bond between Cl and F, with each atom having 3 lone pairs.
    • Formal charge on Cl = 7 - 6 - (1/2 * 2) = 7 - 6 - 1 = 0
    • Formal charge on F = 7 - 6 - (1/2 * 2) = 7 - 6 - 1 = 0
    • Correct Answer: C) 0, 0