PORTAGE LEARNING CHEM 210 - MODULE 2 EXAM

PORTAGE LEARNING CHEM 210 - MODULE 2 EXAM. Scientific Calculator The pH of a solution of 8.9 x 10-12 M NaOH is: A. 8.9 B. 8.9 x 10-12 C. 4.8 D. 11 E. 2.9 A B C D E [Kw=[H+][OH-] = 1.0 x 10-14; [H+][8.9 x 10-12] = 1.0 x 10-14 ;[H+]=890; pH=-log[890]=2.9] Water is a unique molecule. Which of the following contributes to water’s unique place Question 1 3 / 3 pts Question 2 3 / 3 pts in the chemical world? The geometry of the molecule The polarity of the O-H bonds The ability of water molecules to hydrogen bond The bond angle of water All of the answers are correct ALL OF THE ANSWERS ARE CORRECT What factor contributes to the bent shape of a water molecule? The dipole arrows in a water molecule The unshared electron pairs on the oxygen atom The electronegativity difference between hydrogen and oxygen The unequal electron sharing between hydrogen and oxygen None of the answers are correct THE UNSHARED ELECTRON PAIRS ON THE OXYGEN ATOM Which diagrams correctly represent a hydrogen bond? Question 4 3 / 3 pts A and B A and D B and C C and D A and C AAND C BOTH SHOW A PROTON DONOR AND ACCEPTOR Scientific Calculator The H+ concentration of a solution is 5.6 x 10-5 What is the pH? -4.25 4.25 [ [H+]=5.6 x 10-5; pH=-log[5.6 x 10-5]=4.25] 5.65 -9.75 9.75 4.25 [ [H+]=5.6 x 10-5; pH=-log[5.6 x 10-5]=4.25] If the Ka of an acid is 2.67 x 10-5, what is the pKa? 7.45 Question 5 3 / 3 pts 12.25 5.26 2.67 4.57 4.57 [pKa = -log(2.67 x 10-5) = 4.57] List the acids in INCREASING order of strength (weakest to strongest): Nitrous acid (Ka = 4.0 x 10-4); acetic acid (Ka = 1.7 x 10-5); phosphoric acid (Ka = 7.3 x 10-3) Nitrous acid, acetic acid, phosphoric acid Acetic acid, nitrous acid, phosphoric acid Phosphoric acid, nitrous acid, acetic acid Acetic acid, phosphoric acid, nitrous acid None of the above ACETIC ACID, NITROUS ACID, PHOSPHORIC ACID Elemental bromine (Br2) is a liquid at room temperature. What is the dominant attractive force that exists between Br2 molecules in the liquid? Halogen forces Dipole-dipole forces Hydrogen bonds Covalent bonds London forces LONDON FORCES Question 7 3 / 3 pts Question 8 3 / 3 pts Which one of the following molecules can form a hydrogen bond? A. HBr B. HCl C. NH3 D. CH4 E. H2 C. NH3 A hydrogen bond can form between a hydrogen atom bonded to nitrogen, N–H, and . C O Cl P Br O In a bond between P and Cl, there exists a difference in electronegativity resulting in partial positive and partial negative charges. If a dipole arrow were added to this structure, which way would the arrow point? Question 10 3 / 3 pts Question 11 3 / 3 pts The arrow points from Br toward N The arrow points from N toward Br Two arrows; one pointed in each direction There would not be a dipole arrow in this case. None of the above THE ARROW POINTS FROM N TOWARD BR The following reaction occurs in glues purchased from hardware stores. Customers use this product to glue plastic together. Epoxy (l) + hardener (l) ⟶ ⟶ Glue (s) + heat given of What is the sign (+ or -) of the change in Δ ΔG and Question 12 3 / 3 pts Δ ΔH? A) ΔG is (+) and ΔH is (-) B) ΔG is (-) and ΔH is (-) C) ΔG is (-) and ΔH is (+) D) ΔG is (+) and ΔH is (+) E) None of the above B) ΔG is (-) and ΔH is (-) Which of the following is the free-energy change of a reaction? A) G B) ΔS C) ΔH D) ΔG Question 13 3 / 3 pts E) All of the above D) ΔG Which of the following is the change in entropy of a reaction? A) ΔG B) ΔE C) ΔH D) ΔS E) None of the above D) ΔS Question 14 3 / 3 pts Question 15 3 / 3 pts A B C D E D Which buffer system is used by the blood to maintain pH balance? Vinegar buffer system Acetic acid buffer system Bicarbonate buffer system Water buffers system Question 16 3 / 3 pts Formic acid buffer system BICARBONATE BUFFER SYSTEM A buffer can neutralize only a certain amount of acid and base. We say that this is its: Buffer limit Buffer capacity Buffer range Buffer maintenance Buffer arena BUFFER CAPACITY Is a pH of 8.36 acidic, neutral, or basic? Acidic Neutral Basic Both Acidic and Basic Both Neutral and Basic BASIC The “ion product” is equal to what value? Question 17 3 / 3 pts Question 18 3 / 3 pts Question 19 3 / 3 pts A. 1.0 x 10-14 B. 1.0 x 10-7 C. 2.1 x 10-7 D. 5.6 X 10-13 E. None of the above A. 1.0 x 10-14 In equilibrium constant expressions, the concentration is expressed in units of as indicated by the brackets [ ]. molarity acid value base value neutral value None of the above MOLARITY Scientific Calculator A pH = 5.0 indicates a concentration of OH- (in M) of . Question 20 3 / 3 pts Question 21 3 / 3 pts A. 5 B. 10-5 C. 10-9 D. 10-1 E. 101 C. 10-9 The lysosome has a pH of 5.0. Which of the following weak acids would best work to buffer at pH 5.0? Formic Acid Dihydrogen phosphate Propionic acid Tartaric acid All of these Question 22 3 / 3 pts PROPIONIC ACID Which of the following compounds would not be soluble in water? NaCl Oil Glucose NH3 All of the above would be soluble OIL The oxygen in water has what type of hybridization? A. sp B. sp2 C. sp3 D. sp3d E. All of the above C. sp3 Question 23 3 / 3 pts Question 24 3 / 3 pts Four identical molecules dissolve in water. Each molecule contains both a polar portion and nonpolar portion of structure. The four molecules interact in such a way that the nonpolar sections align. This is an example of the . Buffering capacity Hydrophilic effect Hydrogen bonding effect Hydrophobic effect All of the above HYDROPHOBIC EFFECT (Short Response) How does the strength of a hydrogen bond compare to the strength of a London Force? Also, how about the strength of a hydrogen bond compared to a dipole-dipole force? Briefly comment on these differences. The hydrogen bond strength is between 12 and 16 kcal, while the London force is generally less than 1 Kcal. A dipole-dipole bond usually is from 0.5 to 2.0 kcal. Also, hydrogen bonds are the strongest non-covalent force, which is illustrated by these numbers. Scientific Calculator Question 25 3 / 3 pts Question 26 5 / 5 pts Question 27 5 / 5 pts (Fill in the blanks) At cool temperatures, water vapor turns into liquid water releasing heat in the process. Fill in the missing blanks, below, regarding this process. Please identify your answers by writing “A.” then your answer, “B” then your answer, and so Question 28 0 / 5 pts Question 29 5 / 5 pts forth. The free-energy change, ΔG, has a A value (choose “+” or “-“). The enthalpy change, B (fill in symbol), has a C value (choose “+” or “-“). The D change, (ΔS), has a E value (choose “+” or “-“). A) “-“ B) ΔH C) “-“ D) entropy E) “-” (Short Response) A group of molecules forms a clathrate in water. What is a clathrate and why does it form? The hydrophobic effect helps scientists explain how biological molecules form and interact. For instance, when molecules with both a nonpolar and polar regions dissolve in water, the nonpolar regions pack together. The packing of the nonpolar regions minimizes the interaction with water and the polar region interact with water, which in total is called the hydrophobic effect. The driving force behind this effect is the spontaneous drive of water to bind to itself through hydrogen bonds. To maximize the hydrogen bonds, water orders itself around the hydrophobic portion of the nonpolar regions in a cage structure also called a clathrate. In so doing, water can form bonds with itself and also permit the nonpolar regions to be dissolved. Question 30 5 / 5 pts