CHEM210 / CHEM 210 Module 2: (Latest Update 2026 / 2027) Organic Chemistry | Questions & Answers | Grade A | 100% Correct – Portage Learning

CHEM210 / CHEM 210 Module 2: (Latest Update 2026 / 2027) Organic Chemistry | Questions & Answers | Grade A | 100% Correct – Portage Learning Q: Which of the following mol- ecules can form a hydrogen bond? A. HBr B. HCl C. NH3 D. CH4 E. H2 Answer C. NH3 Q: The pH of a solution of 0.0010 M NaOH is: A. 1 B. 11 C. 8 D. 0 E. 14 Answer B.11 1.0 x 10^-14 = [H+][OH-] 1.0 x 10^-14 = [H+][0.0010] 1.0 x 10^-14 /0.0010 1.0 x 10^-11 = H+ pH = -log[1.0 x 10^-11] = 11 Q: The pH of a solution of 8.9 x 10-12M NaOH is: A. 8.9 B. 8.9 x 10^-12 C. 4.8 D. 11 E.2.9 Answer E. 2.9 Kw=[H+][OH-] 1.0 x 10^-14= [H+][8.9 x 10^-12] [H+]=890 pH=-log[890] 2.9 Q: The pH of a solution of 3.2 x 10^-10 M NaOH is: A. 3.7 B. 3.7 x 10^-10 C. 4.5 D. 13 E. 8.7 Answer C. 4.5 1.0 x 10^-14 = [H+][OH-] 1.0 x 10^-14 = [H+][3.2 x 10^-10] 1.0 x 10^-14/3.2 x 10^-10 = [H+] 3.25 x 10^-5 = [H+] pH = -log [H+] pH = -log [3.25 x 10^-5] pH = 4.5 Q: Water is a unique molecule. Which of the following con- tributes to water's unique place in the chemical world? A. The geometry of the molecule B. The polarity of the O-H bonds C. The ability of water molecules to hydrogen bond D. The bond angle of water E. All of the answers are correct Answer E. All of the answers are correct Q: What factor contributes to the bent shape of a water molecule? A. The dipole arrows in a water molecule B. The unshared electron pairs on the oxygen atom C. The electronegativity differ- ence between hydrogen and oxy- gen D. The unequal electron sharing between hydrogen and oxygen E. None of the answers are cor- rect Answer B. The unshared electron pairs on the oxygen atom Q: The H+ concentration of a solu- tion is 5.6 x 10^-5. What is the pH? A. -4.25 B. 4.25 C. 5.65 D. -9.75 Answer E. 9.75 B. 4.25 [H+] = 5.6 x 10^-5 pH = -log[5.6 x 10^-5] = 4.25 Q: The H+ concentration of a solution is 1.2 x 10^-3 M. What is the pH? Answer 2.92 pH = -log [H+] pH = -log[1.2 x 10^-3] pH = 2.92 Q: The H+ concentration of a solution is 9.9 x 10^-8 M. What is the pH? Answer 7.0 pH= -log[H+] pH=-log[9.9 x 10-8] pH=7.0 Q: If the Ka of an acid is 7.45 x 10^-10, what is the pKa? A. 7.45 B. 2.25 C. 6.38 D. 9.13 E. -7.45 Answer D. 9.13 [pKa = -log(7.45 x 10^-10) = 9.13] Q: If the Ka of an acid is 5.63 x 10-3, what is the pKa? Answer 2.25 Q: If the Ka of an acid is 2.67 x 10, what is the pKa? A. 7.45 B. 12.25 C. 5.26 D. 2.67 E. 4.57 Answer E. 4.57 pKa = -log(2.67 x 10) 4.57 Q: List the acids in INCREASING order of strength (weakest to strongest): Nitrous acid (Ka = 4.0x10^-4); Acetic acid (Ka = 1.7x10^-5); Phosphoric acid (Ka = 7.3x10^-3) A. Nitrous acid, acetic acid, phosphoric acid B. Acetic acid, nitrous acid, phosphoric acid C. Phosphoric acid, nitrous acid, acetic acid D. Acetic acid, phosphoric acid, nitrous acid E. None of the above Answer B. Acetic acid, nitrous acid, phosphoric acid Q: List the acids in DECREASING order of strength (strongest to weakest): Answer Nitrous acid (Ka = 4.0 x 10-4); acetic acid (Ka = 1.7 x 10-5); phosphoric acid (Ka = 7.3 x 10-3) Phosphoric acid, nitrous acid, acetic acid Q: Elemental iodine (I2) is a solid at room temperature. What is the dominant attractive force that ex- ists between I2 molecules in the solid? A. London forces B. Hydrogen bonds C. Halogen forces D. Dipole-dipole forces E. Covalent bonds Answer A. London forces Q: Elemental bromine (Br2) is a liquid at room temperature. What is the dominant attractive force that exists between Br2 molecules in the liquid? A. Halogen forces B. Dipole-dipole forces C. Hydrogen bonds D. Covalent bonds E. London forces E. London forces Which one of the following molecules can form a hydrogen bond? A. HI B. HCl C. N2 D. CH4 E. H2O C. N2 A hydrogen bond can form be- tween a hydrogen atom bonded to Oxygen, O-H, and __________. A. C B. B C. Cl D. P E. N E. N A hydrogen bond can form between a hydrogen atom bondedto nitrogen, N-H, and ________. O In a bond between P and Cl, there exists a difference in the electronegativity resulting in partial positive and partial negative charges. If a dipole arrow were added to this structure, which was would the arrow point? A. The arrow points from Br to- ward N B. The arrow points from N to- ward Br C. Two arrows; one pointed in each direction D. There would not be a dipole arrow in this case E. None of the above B. The arrow points from N toward Br The following reaction occurs in glues purchased from hardwarestores. Customers use this prod-uct to glue plastic together. Epoxy (l) + hardener (l) -- Glue (s) + heat given off What is the sign (+ or -) of the change in delta G and delta H? A. delta G is (+) and delta H is (-) B. delta G is (+) and delta H is (+) C. delta G is (-) and delta H is (+) D. delta G is (-) and delta H is (-) E. None of the above D. delta G is (-) and delta H is (-) Which of the following is the free-energy change of a reaction? A. G B. S C. H D. F E. All of the above. A. G Which of the following is the change in entropy of a reaction? A. G B. E C. H D. S E. None of the above. D. S Which of the following is the change in entropy of a reaction? A. G B. E C. H D . F E. None of the above E. None of the above Which buffer system is used by the blood to maintain pH balance? A. Vinegar buffer system B. Acetic acid buffer system C. Bicarbonate buffer system D. Water buffers system E. Formic acid buffer system C. Bicarbonate buffer system Which buffer system is used by the renal system to maintain pH balance? Bicarbonate buffer system A buffer can neutralize only a certain amount of acid and base. We say that this is its: A. Buffer limit B. Buffer range C. Buffer maintenance D. Buffer capability E. Buffer capacity E. Buffer capacity Is a pH of 3.91 acidic, neutral, or basic? A. Acidic B. Neutral C. Basic D. Both acidic and basic E. Both neutral and base A. Acidic Is a pH of 7.00 acidic, neutral, or basic? Neutral Is a pH of 8.36 acidic, neutral, or basic? Basic The "ion product" is equal to what value? A. 1.0 x 10^-4 B. 1.0 x 10^-14 C. 2.1 x 10^-7 D. 5.6 X 10^-13 E. None of the above B. 1.0 x 10^-14 In equilibrium constant expressions, the double brackets [ ] indicate: Concentration in molarity In equilibrium constant expressions, the concentration is expressed in units of _______ as indicated by the brackets [ ]. A. molarity B. acid value C. base value D. neutral value E. None of the above A. Molarity A pH = 5.0 indicates a concentra- tion of OH- (in M) of __________. A.5 B. 10^-5 C. 10^-9 D. 10^-1 E. 101 C. 10^-9 H+OH= 14 14-5 = OH 9 = OH [OH] = 1.0 x 10^-9 A student needs to make a buffer pH of 3.2. Which of the following would best work to buffer at pH 3.2? Tartaric Acid A student needs to make a buffer pH of 4.0. Which of the following would best work to buffer at pH 4.0? Formic Acid The lysosome has a pH of 5.0. Which of the following weak acids would best work to buffer at pH 5.0? A. Formic Acid B. Dihydrogen phosphate C. Propionic acid D. Tartaric acid E. All of these C. Propionic acid Which of the following compounds would not be soluble in water? A. NaCl B. Oil C. Glucose D. NH3 E. All of the above would be soluble B. Oil Which of the following compounds would not be soluble in water? A. NaCl B. OH C. Glucose D. Wax E. All of the above would be soluble D. Wax The hybridization of the central atom in water is ________. A. s B. sp C. sp2 D. sp3 E. None of the above D.sp3 Three identical molecules dissolve in water. Each molecule contains both a polar portion and non-polar portion of structure. The three molecules interact in such a way that the non-polar sections align. This is an example of the _________. A. Buffering capacity B. Hydrophilic effect C. Hydrogen bonding effect D. Hydrophobic effect E. All of the above D. Hydrophobic effect (Short Response) How does the strength of a covalent bond compare to the strength of London Forces and hydrogen bonds? Briefly comment on these differences. A typical covalent bond is around 400 kcal, while a London force is less than1 kcal. So, a covalent bond is at least 400 times the size a London force. The hydrogen bond strength is between 12 and 16 kcal, which makes the covalent bond about 40 times a hydrogen bond. More over, hydrogen bonds are the strongest non-covalent force, so this is significant. (Short Response) How does the strength of a hydrogen bond compare to the strength the London Force? Also, how about the strength of a hydrogen bond compare to a dipole-dipole force? Briefly comment on these differences. Hydrogen bond strength is between 12-16 kcal; London force is 1 Kcal; dipole-dipole bond is 0.5-2.0 kcal. Hydro- gen bonds are the strongest non-covalent force. (Short Response) What is the hy- drophobic effect and how does a clathrate help explain this phe- nomenon? When molecules with both a non-polar and polar regions dissolve in water, the non polar regions pack together to minimize the interaction with water and the polar region interact with water, which is called the hydrophobic effect. The driving force of the 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 non polar 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. Short Response) The weak acid HX has the following equilibrium reaction with 0.64M HX, 0.55M X-, and 0.55M H+. Cal- culate the Ka for this hypothetic com- pound. Show your work. HX = H+ + X- Ka= [X-][H+]/ HX; Ka = 0.55 x 0.55 / 0.64; Ka = .4727 The weak acid HX has the following equi- librium reaction with 0.051M HX, 0.32M X-, and 0.32M H+. Calculate the Ka for this hypothetic compound. Show your work.HX = H+ + X- Ka= [X-][H+]/ HX; Ka = 0.32 x 0.32 / 0.051 Ka = 2.0 (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 forth. The free-energy change, ”G, has a _____A______ value (choose "+" or "-"). The enthalpy change, __B___ (fillin symbol), has a ___C_____ value (choose "+" or "-"). The _____D______change, (”S), has a ______E_____ value (choose "+" or "-"). A) - B) H C) - D) entropy E) - (Short Response) Use the general ioniza- tion equation for a weak acid to show how a buffer resists changes to the addition of Acid The conjugate base A- reacts with added H+ to form weak which neutralizes the acid and maintains the pH. aqueous solution water based environments, solution which. the solvent is water water unique molecule that contains only non metal elements covalently bonded as H2O daily water intake for human 1-2 l for a typical human Water is made of two non metal elements Autoionization is a compound ability to react. with itself to form ions high melting point or boiling point indicates molecule has stronger intermolecular forces such as H2O dipole arrow the arrows points to the more electronegative atom, in. H2O hydrogen points to oxygen, resulting polarity for. water Non-covalent forces forces that occur between two molecules What natural phenomena help illustrate the attractive forces? -water beading. up. on a waxed car - oil and water separating in italian dressing - fat soluble vitamins dissolving in the cellular membrane Partial charges occur when ... a covalent bond links atoms of two kinds and atoms share electrons unequally. What. are the three types of non-covalent forces scientist typically talk about? 1. dipole-dipole forces 2. hydrogen bonding 3. london dispersion forces dipole-dipole interactions two molecules align their dipoles to generate an attraction - strongest class of intermolecular forces, -liquid form such as acetone and glucose hydrogen bonds strongest dipole-dipole intercation -attractive forces result to a + and - partial charges what are the 2 parts for a hydrogen bond to occur ? 1. hydrogen. atom must serve as a donor ( partial +) gen acceptor must be present ( partial-) Hydrogen donor A substance or compound that gives up or transfers a hydrogen atom to another substance - such a s nitrogen, oxygen or fluorine. hydrogen acceptor pair of non bonded electrons on a separate oxygen, nitrogen or fluorine how many bonds does hydrogen form when it freezes ? about 4 in a single ice water molecule London forces weakest interaction - temporary transient arrangement of electrons within a. molecule resulting in a small but essential, partial + and partial - charges - interaction between two. atoms or molecules how strong is O-H compare to others? is about 400 times stronger than a LONDON FORCE 200 times as DIPOLE-DIPOLE force 40 times of hydrogen bond Pros of non covalent bonds These forces between molecules are weaker, which permits them to break and reform easily. This breaking and reforming of non-covalent permits many types of processes, such as drugs binding to proteins, to occur again and again in the Hydrophilic water loving, molecules interact with water through dipole dipole interactions or hydrogen bonds hydrophobic water hating, london forces - separation on water and oil , is bc water pushes oil molecules away Clathrate water orders itself around the hydrophobic portion of the nonpolar regions in a cage structure hydrophobic effect The packing of the nonpolar regions minimizes the interaction with water, while the polar region interacts with water Acetic acid, carbon dioxide and histidine, react with water to produce slightly acidic solution Equilibrium condition achieved when the. rates of the forward and reverse reactions are equal equilibrium constant Keq which describes the extent to which the reaction proceeds in the forward direction Whats the pH of the cytoplasm for a typical human cell ? 7.4, physiological pH physiological pH near the neutral pH of 7.0 on the pH scale Lysosome pH 5.0, acidic strong acids compounds such as hydrochloric acid and sulfuric acid that can both dissolve in water strong bases sodium hydrocide and calcium hydroxide also dissolve and completely ionize in solutions weak acids and weak bases fail to dissociate completely, but only partially. ionize in solution Proton acceptor A substance that takes up hydrogen ions in detectable amounts. Commonly referred to as a base. proton donor acid, generated an H in reaction Large value of Ka strong acid, higher concentration of H smaller pKa stronger acid buffer an aqueous system that resist changes in pH when small amounts of acid or base which buffer aids the cell in maintaining the pH in the cytoplasm? dihydrogen phosphate 7.4 buffering range the pH range the buffer can be effective buffering capacity the amount of acid or base a buffer can neutralize entropy A measure of disorder or randomness. if a reaction produces more products than reactant, then an increase in ? entropy has occured f the reaction contains structurally ordered reactants, such as solids, and produces liquids or gases, then there is also an increase in entropy free energy content G The component of the total energy of a system that can do work at constant temperature and pressure. What properties does water contribute in chemical world? - high melting point and boiling point than other compounds - the geometry of the molecule -polarity of O-H binds -ability of water molecules to hydrogen bond - bond angle of water The pH of a solution of 0.0010 M NaOH is: 11 (Kw=[H+][OH-] = 1.0 x 10-14; [H+][0.0010] = 1.0 x 10-14 [H+]=1.0 x 10-11; pH= log[1.0 x 10-11]=11) Water is a unique molecule. Which of the following contributes to water's unique place in the chemical world? All of the answers are correct The bent shape of water is due to ______________. The unshared electron pairs on the oxygen atom Which diagrams correctly represent a hydrogen bond? A and D The H+ concentration of a solution is 1.2 x 10-3 M. What is the pH? 2.92 If the Ka of an acid is 5.63 x 10-3, what is the pKa? 2.25 ([pKa = -log(5.63 x 10-3) = 2.25]) List the acids in DECREASING order of strength (strongest to weakest): Nitrous acid (Ka = 4.0 x 10-4); acetic acid (Ka = 1.7 x 10-5); phosphoric acid (Ka = 7.3 x 10-3) Phosphoric acid, nitrous acid, acetic acid Elemental iodine (I2) is a solid at room temperature. What is the dominant attractive force that exists between I2 molecules in the solid? London forces 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 oxygen, O-H, and ________. N 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? 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 off What is the sign (+ or -) of the change in Δ G and Δ H? Δ G is (-) and Δ H is (-) Which of the following is the free-energy change of a reaction? Δ G Which of the following is the change in entropy of a reaction? None of the above A Which buffer system is used by the renal system to maintain pH balance? Bicarbonate buffer system A buffer can neutralize acid and base within a certain limit. We say that this is its: Buffer capacity Is a pH of 8.36 acidic, neutral, or basic? Basic The "ion product" is equal to what value? 1.0 x 10-14 In equilibrium constant expressions, the concentration is expressed in units of _______ as indicated the by the brackets [ ]. Molarity A pH = 5.0 indicates a concentration of OH- (in M) of __________. 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? Propionic acid Which of the following compounds would not be soluble in water? Wax The oxygen in water has what type of hybridization? C. sp3 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 _________. Hydrophobic effect (Short Response) How does the strength of a hydrogen bond compare to the strength the London Force? Also, how about the strength of a hydrogen bond compare to a dipole-dipole force? Briefly comment on these differences. Hydrogen bond strength is between 12-16 kcal; London force is 1 Kcal; dipole-dipole bond is 0.5-2.0 kcal. Hydrogen bonds are the strongest non-covalent force. (Short Response) The weak acid HX has the following equilibrium reaction with 0.64M HX, 0.55M X-, and 0.55M H+. Calculate the Ka for this hypothetic compound. Show your work. HX = H+ + X- Ka= [X-][H+]/ HX; Ka = 0.55 x 0.55 / 0.64; Ka = .4727 (no units) (Short Response) Use the general ionization equation for a weak acid to show how a buffer resists changes to the addition of Acid (H+). HA = A- + H+ The conjugate base A- reacts with added H+ to form weak which neutralizes the acid and maintains the pH. (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 forth. "The free-energy change, Δ G, has a _____A______ value (choose "+" or "-"). The enthalpy change, __B__ (fill in symbol), has a ___C_____ value (choose "+" or " "). The _____D______change, (Δ S) has a ______E_____ value (choose "+" or "-")." A) - B) Δ H C) -D) entropy E) - (Short Response) What is the hydrophobic effect and how does a clathrate help explain this phenomenon? The hydrophobic effect explains how biological molecules form and interact. When molecules with both a nonpolar and polar regions dissolve in water, the nonpolar regions pack together. Water orders itself around the hydrophobic portion of the nonpolar regions in a cage structure, called a clathrate, forming bonds with itself and also permit the nonpolar regions to be dissolved. The pH of a solution of 0.0010 M NaOH is: 1 11 8 0 14 11 [Kw=[H+ ][OH- ] = 1.0 x 10-14; [H+ ][0.0010] = 1.0 x 10-14 [H+ ]=1.0 x 10-11; pH= log[1.0 x 10-11;]=11] Water is a unique molecule. Which of the following contributes to water's unique place 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 The bent shape of water is due to ______________. - The dipole arrows in a water molecule - - The electronegativity difference between hydrogen and oxygen - The unequal electron sharing between hydrogen and oxygen - The unshared electron pairs on the oxygen atom - None of the answers are correct - The unshared electron pairs on the oxygen atom The H+ concentration of a solution is 1.2 x 10-3 M. What is the pH? -1.20 1.20 3.12 -2.92 2.92 2.92 If the Ka of an acid is 5.63 x 10-3, what is the pKa? 6.86 2.25 5.63 10.12 1.38 2.25 [pKa = -log(5.63 x 10-3) = 2.25] List the acids in DECREASING order of strength (strongest to weakest): 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 - Phosphoric acid, nitrous acid, acetic acid Elemental iodine (I2) is a solid at room temperature. What is the dominant attractive force that exists between I2 molecules in the solid? - London forces - Hydrogen bonds - Halogen forces - Dipole-dipole forces - Covalent bonds - London forces Which one of the following molecules can form a hydrogen bond? A. HBr B. HCl C. NH3 D. CH4 E. H C. NH3 A hydrogen bond can form between a hydrogen atom bonded to oxygen, O-H, and ________. C B Cl P N N dipole arrow points towards negative side 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 off What is the sign (+ or -) of the change in Δ G and Δ H? A) Δ G is (+) and Δ H is (-) B) Δ G is (-) and Δ H is (-) C) Δ G is (-) and Δ H is (+) D) Δ G is (+) and Δ H is (+) E) None of the above B) Δ G is (-) and Δ H is (-) Which of the following is the free-energy change of a reaction? A) Δ G B) Δ S C) Δ H D) Δ F E) All of the above A) Δ G Which of the following is the change in entropy of a reaction? A) Δ G B) Δ E C) Δ H D) Δ F E) None of the above E) None of the above equilibrium constant expression the ratio of the equilibrium concentrations or partial pressures of products to reactants, each term raised to a power equal to the coefficient of that substance in the balanced chemical equation for the reaction Which buffer system is used by the renal system to maintain pH balance? - Phosphate buffer system - Acetic acid buffer system - Water buffers system - Formic acid buffer system - Bicarbonate buffer system - Bicarbonate buffer system A buffer can neutralize acid and base within a certain limit. 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? A. 1.0 x 10-4 B. 1.0 x 10-14 C. 2.1 x 10-7 D. 5.6 X 10-13 E. None of the above B. 1.0 x 10-14 In equilibrium constant expressions, the concentration is expressed in units of _______ as indicated the by the brackets [ ]. molarity acid value base value neutral value None of the above molarity A pH = 5.0 indicates a concentration of OH- (in M) of __________. 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 Propionic acid Which of the following compounds would not be soluble in water? A. NaCl B. OH C. Glucose D. Wax E. All of the above would be soluble D. Wax The oxygen in water has what type of hybridization? A. sp B. sp2 C. sp3 D. sp3 d E. All of the above C. sp3 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 How does the strength of a hydrogen bond compare to the strength the London Force? Also, how about the strength of a hydrogen bond compare to a dipole-dipole force? Briefly comment on these differences. London forces are the weakest non covalent force and hydrogen bonds are the strongest of the non covalent forces. Dipole dipole forces are the second strongest non covalent forces. 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 forth. The free-energy change, Δ G, has a ____A_______ value (choose "+" or "-"). The enthalpy change, ___B__ (fill in symbol), has a ____C____ value (choose "+" or "-"). The _____D______change, ( Δ S) has a _____E______ value (choose "+" or "-"). A: - B: + C: - D: entropy E: - What is the hydrophobic effect and how does a clathrate help explain this phenomenon? - helps scientists explain how biomolecules form and interact - molecules with polar and nonpolar regions in water, nonpolar regions pack together to minimize interaction with h2o and lets polar region interact - water drives this by binding to itself through hydrogen bonds - maximizes hydrogen bonds by ordering itself around hydrophobic portion of non polar region and form strucutre called a calthrate - water can form bonds with iself and allow nonpolar regions to dissolve The pH of a solution of 3.2 x 10-10 M NaOH is: A. 3.7 B. 3.7 x 10-10 C. 4.5 D. 13 E. 8.7 C. 4.5 Kw=[OH][H] pH=-log[H] Which attribute contributes to water's unusual properties? A. The geometry of the molecule B. The polarity of the O-H bonds C. The ability of water molecules to hydrogen bond D. The bond angle of water E. All of the answers are correct E. All of the answers are correct What factor contributes to the bent shape of a water molecule? The unshared electron pairs on the oxygen atom Which diagrams correctly represent a hydrogen bond? A and D H-bonding: Donors: OH, NH, FH Acceptors: O, N, H The H+ concentration of a solution is 5.6 x 10-5 What is the pH? 4.25 -log[H]=pH If the Ka of an acid is 7.45 x 10-10, what is the pKa? 9.13 pKa=-log[Ka] 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) Acetic acid, nitrous acid, phosphoric acid larger value of Ka means a stronger acid smaller pKa value indicates a stronger acid Elemental bromine (Br2) is a liquid at room temperature. What is the dominant attractive force that exists between Br2 molecules in the liquid? London Forces- temporary partial charges from random movement of e- Which one of the following molecules can form a hydrogen bond? A. HI B. HCl C. N2 D. CH4 E. H2O C. N2 NOF A hydrogen bond can form between a hydrogen atom bonded to oxygen, O-H, and ________. N/ O, F 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? The arrow points from N toward Br Arrow points towards negative partial 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 off What is the sign (+ or -) of the change in ΔG and 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 (-) ΔGibbs free energy:(+)non-spontaneous (-)spontaneous ΔH Enthalpy:(+)endothermic, heat entering (-)exothermic, heat leaving(more common) ΔS Entropy: (+)breaking bonds (-)forming bonds Which of the following is the free-energy change of a reaction? A) ΔG B) ΔS C) ΔH D) ΔF E) All of the above A. ΔG Which of the following is the change in entropy of a reaction? A) ΔG B) ΔE C) ΔH D) ΔF E) None of the above E. None of the above Which buffer system is used by the renal system to maintain pH balance? Bicarbonate buffer system A buffer can neutralize only a certain amount of acid and base. We say that this is its: Buffer Capacity Is a pH of 3.91 acidic, neutral, or basic? Acidic The "ion product" is equal to what value? A. 1.0 x 10-4 B. 1.0 x 10-14 C. 2.1 x 10-7 D. 5.6 X 10-13 E. None of the above B. 1.0 x 10-14 In equilibrium constant expressions, the double brackets [ ] indicate: Concentration in molarity A pH = 5.0 indicates a concentration of OH- (in M) of __________. A. 5 B. 10-5 C. 10-9 D. 10-1 E. 101 C. 10-9 Use anti log and Kw A student needs to make a buffer pH of 3.2. Which of the following would best work to buffer at pH 3.2? Tartaric Acid which ever pKa closely matches Acetic acid pKa=4.74 Formic acid =3.74 Dihydrogen phosphate= 7.21 Propionic acid= 4.89 Tartaric acid = 3.00 Which of the following compounds would not be soluble in water? Oil SOLUBLE: ionic: ex. KCl Polar: ex. acetone, HCl H-Bonding: sugars, acetic acid. The hybridization of the central atom in water is ________. A. s B. sp C. sp2 D. sp3 E. None of the above D. sp3 Three identical molecules dissolve in water. Each molecule contains both a polar portion and nonpolar portion of structure. The three molecules interact in such a way that the nonpolar sections align. This is an example of the _________. Hydrophobic effect (Short Response) How does the strength of a covalent bond compare to the strength of London Forces and hydrogen bonds? Briefly comment on these differences. A typical covalent bond is around 400 kcal, while a London force is less than 1 kcal. So, a covalent bond is at least 400 times the size a London force. The hydrogen bond strength is between 12 and 16 kcal, which makes the covalent bond about 40 times a hydrogen bond. Moreover, hydrogen bonds are the strongest non covalent force, so this is significant. Break and form bonds easily. LF:1 D-D:0.5-2 H-Bond:12-16 Covalent: 400 + (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 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) What is the hydrophobic effect and how does a clathrate help explain this phenomenon? 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. show how a buffer resists change to the addition of a base OR show how a buffer resists change to the addition of a acid Weak acid, HA, reacts with added OH to form water. This neutralizes the base and maintains the pH acid added to the system is neutralized by the conjugate base, which we also called the proton acceptor. Buffering works best when the concentrations of the weak acid and conjugate base are equal.