MCAT Practice Questions and Correct Answers Graded A+

Coordination compounds, a .k.a. coordinate covalent bonds, are? Coordinate covalent bonds usually occurs between? Does B have a lone pair? - - bonds in which one atom donates BOTH of the electrons necessary to form a sigma bond - a transition metal with a positive oxidation state and an atom containing a lone pair - no Which of the following is most likely to form a coordination compound with nickel? A. CH4 B. BF3 C. PH3 D. NH4+ - - C. PH3 The action that will increase the pressure in a reaction vessel is any disturbance that will push the equilibrium TOWARD? 3H2(g) + N2(g) <=> 2NH3(g), how many moles does the reactant side and product side have? To increase pressure, towards what side would you want to push the reaction? - - the side of the reaction containing more moles of gas - 4 and 2 respectably - toward the left, it has more moles Given the following balanced reaction occurring in a vessel of constant volume, which of the following actions would cause the greatest increase in pressure inside the reaction vessel? 3H2(g) + N2(g) <=> 2NH3(g) A. Adding more H2 B. Adding more NH3 C. Removing NH3 D. Adding more N2 - B. Adding more NH3 What is a hydride? The element that will form the most polar acid hydride will be the one that is the most? Atoms with the largest or smallest radius and with the highest or lowest ionization energy will be the most electronegative? - - is the anion of hydrogen, H−, or, more commonly, it is a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties - electronegativity - smallest radius and largest ionization Which of the following statements is/are NOT true of the equilibrium constant, Keq? I. Increasing temperature changes Keq II. Increasing temperature has no effect on Keq III. Changing the initial concentration of products or reactants changes Keq A. I only B. II & III C. III only D. I, II & III - - B. II & III Which of the following statements concerning quantum numbers is NOT accurate? A. The principle quantum number is proportional to the energy level of the atom B. The azimuthal quantum number describes the subshell where the electron is located C. The magnetic quantum number specifies which of the orbitals holds the electron D. The electron spin quantum number differentiates between two electrons in the same orbital - A) is only generally true. Recall that a 3d orbital is actually higher in energy than a 4s. The remaining three answer choices are all completely accurate regarding quantum numbers —make sure you know them! The azimuthal quantum number describes? The magnetic quantum number specifies? The electron spin quantum number differentiates between? - - the subshell where the electron is located - which of the orbitals holds the electron - two electrons in the same orbital When a metal reacts violently with water it is because? What provides best explanation of a metals reactivity with water electronegativity or ionization energy? - - the metal is ionizing, or releasing electrons - ionization energy, water reacting with metal is ionization The reactivity of metals with water increases going down a family in the periodic table. This trend is best explained by: A. Increasing flash point B. Increasing electron affinity C. Decreasing electronegativity D. Decreasing ionization energy - D. Decreasing ionization energy Whats the best way to solve this problem? Calcium reacts violently with water and evolves a gas in the process. Which of the following equations most likely represents the reaction between calcium metal and water? A. Ca2+ + H2O(l) → H2(g) + CaO(s) B. Ca(s) + 2H2O(l) → Ca2+ + H2(g) + 2OHC. Ca(s) + H2O(l) → H2O(g) + Ca2+ D. Ca2+ + 2H2O(l) → Ca(s) + 2H2(g) + O2(g) - - Don't be intimidated by this type of question. Look at your possibilities and rule out nonsense . Since we were told that solid calcium, not ionic calcium, is reacting with water, rule out A and D. Answer choice B shows water turning from liquid to vapor apparently spontaneously as solid calcium loses two electrons to form Ca 2+. If you didn't know it already, REDOX reaction always occur in pairs. Things don't lose electrons unless they go ONTO something else that is reduced. As a good exercise, try tracking where the electrons are going in the reaction for answer B, which is the correct answer NH3 is a liquid at room temperature, while AsH3 is a gas. Differences in which of the following best accounts for this observation? B is the correct answer, explain why? A. Electronegativity B. Intermolecular forces C. Ionization energy D. Molecular weight - - it is a better answer because it is more general and would include all of the intermolecular forces that usually account for a compound's state as solid, liquid, or gas