MCAT General Chemistry Practice Exam
Questions And Correct Answers
Which of the following statements accurately describes the difference between a sigma (σ) and a
pi (π) bond?
A. Pi bonds form from the side-to-side overlap of hybridized sp, sp^2, sp^3 superscript orbitals.
B. Sigma bonds form from the end-to-end overlap of two hybridized s or p orbitals.
C. The maximum number of σ versus π bonds between two atoms are different, but the energy
level of the two bonds are the same.
D. Only sigma bonds use hybridized orbitals to overlap in forming the bond. - answer✔✔Only
sigma bonds use hybridized orbitals to overlap in forming the bond.
In regards to the total possible number of bonds between two atoms, the total possible number of
bonds for a σ bond is one and for a π bond is two. In regards to the energy level, a sigma bond is
lower in energy than a π bond.
A sigma σ bond will form from an end-to-end overlap of an s, p, or hybridized orbital.
A π bond will only form from the side-to-side overlap of two unhybridized p orbitals.
Since π bonds only use unhybridized orbitals, only sigma bonds use hybridized orbitals to
overlap in forming the bond. It is the correct answer.
Suppose a weak acid has a Ka = 4.0 x 10^-9. Which of the following gives its equivalent Kb?
Kw = 10^-14
Ka x Kb = Kw
(10^-14) / (4.0 x 10^-9) = 2.5 x 10^-6
Which of the following best describes a chemical species that is measured to have Kb = 3.2 x
10^-18?
A strong base
A weak base
A strong acid
A weak acid - answer✔✔A strong acid
Whether a chemical is an acid or base depends on whether Ka or Kb is greater
Because Ka x Kb = Kw, Ka = 2.3 x 10^3, suggesting that it is an acid
Because Ka >> 1, it is a strong acid
What is the pH of a solution with a hydronium concentration [H3O+] = 10^4 M
-4
-8
10
4 - answer✔✔pH is the negative logarithm of the molar concentration of hydrogen ions
Equivalently, the pH is the logarithm of the molar concentration of hydronium
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