*VI-1 C NC I-3 C NC V-2 C NC **VI-2 C NC I-4 C NC V-3 C NC IX-1 C NC II-2 C NC VII-1 C NC IX-2 C NC V-1 C NC VII-2 C NC

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1 *VI-1 C NC I-3 C NC V-2 C NC **VI-2 C NC I-4 C NC V-3 C NC IX-1 C NC II-2 C NC VII-1 C NC IX-2 C NC V-1 C NC VII-2 C NC Chemistry 131 Quiz 7 Summer 2011 Form B NAME: Key Chapter 16. Reaction Rates and Equilibrium *A. (2.0 pts) Determine whether each reaction shown below will be exothermic or endothermic, and whether K eq will be greater or less than one. 1. Al 2 O 3 (s) + electrical energy 4 Al(s) + 3 O 2 (g) Is the reaction endothermic or exothermic? Endothermic Is K eq greater or less than one? K eq < NO 2 (g) + H 2 O(l) 2 HNO 3 (aq) + NO(g) H = kj Is the reaction endothermic or exothermic? Exothermic Is K eq greater or less than one? K eq > 1 B. (1.0 pts) Calculate the equilibrium constants for the reaction given below. Show your work. PCl 5 (g) PCl 3 (g) + Cl 2 (g) [PCl 5 ] = 8.3 x 10 3 M [PCl 3 ] = 1.5 x 10 2 M [Cl 2 ] = 3.2 x 10 2 M 5.8 x 10 2 = K eq = [PCl 3 ] [Cl 2 ] = 1.5 x 10 2 x 3.2 x 10 2 = 5.8 x 10 2 = [PCl 5 ] (8.3 x 10 3 )

2 **C. (2.0 pts) In class, we discussed the reaction of hydrogen (H 2 ) and iodine (I 2 ) to form hydrogen iodide (HI) The equation for the reaction is shown below: H 2 (g) + I 2 (g) 2 HI(g) = kj colorless violet colorless How will the equilibrium concentrations of the reactants and products change to relieve each of the stresses listed below? Choose your answer from the following selections, and write it in the space provided. No other answers will be accepted. Shifts toward products No effect Stress Add H 2 Add HI Add I 2 Remove H 2 Remove I 2 Remove HI Heat the mixture Cool the mixture Add a catalyst Increase the pressure 5 or more right for competency. Effect on Equilibrium Shifts toward products Shifts toward products Shift toward products Shifts towards products No effect No effect Chapter 14. Acids and Bases D. (2.4 pts) For each solution, fill in the blanks. [H 3 O 1+ ] [OH 1- ] ph Is the solution acidic, basic, or neutral? x 10 4 M 5.0 x M 3.70 Acidic 2. 1 x 10 8 M 1 x 10 6 M 8.0 Basic x x Basic x 10 7 M 1.00 x 10 7 M Neutral One row (not #4) must be all correct for competency. Scoring: 0.6 points per row; 0.1 pt for acidity, 0.2 pts for numbers, 0.1 pt for SF

3 E. (0.8 pts) For each reaction listed below, select the acid, the base, the conjugate acid, and the conjugate base. Write the formula in the space provided. 1. HPO 4 2 (aq) + H 3 O 1+ (aq) H 2 PO 4 1 (aq) + H 2 O(l) The acid H 3 O 1+ The conjugate base H 2 O The base HPO 4 2 The conjugate acid H 2 PO H 2 C 2 O 4 (aq) + H 2 O(l) HC 2 O 4 1 (aq) + H 3 O 1+ (aq) The acid H 2 C 2 O 4 The conjugate base HC 2 O 4 1 The base H 2 O The conjugate acid H 3 O 1+ F. 1. (1 pt) When HCl(aq) is added to each of the following buffer systems, which component reacts with it? HPO 4 2 H 2 PO and HPO 4 S 2 HS 1 and S 2 2. (1 pt) When NaOH(aq) is added to each of the following buffer systems, which component reacts with it? NH 1+ 4 and NH 3 HCO and CO 3 One example in each group must be correct for the competency. 1+ NH 4 1 HCO 3 3. (0.4 pt) Phenol is also called carbolic acid, and it was the first antiseptic used in surgery. K a for phenol is 1.3 x What is the ph of a buffer made from equal volumes of 0.1 M phenol and 0.1 M phenoxide (the conjugate base of phenol)? 9.89

4 Competencies from previous quizzes: I-3 Sulfuryl chloride contains % Cl, 23.71% O, and 23.76% S. What is its empirical formula? Show your work. SO 2 Cl g Cl x 1 mol Cl = mol Cl mol Cl = mol Cl = 2 Cl g Cl mol S mol S 1 S g O x 1 mol O = mol O mol O = mol O = 2 O g O mol S mol S 1 S g S x 1 mol S = mol S SO 2 Cl g S I-4 Cyanuric acid is a precursor to bleaches, disinfectants, and herbicides. Its molar mass is g/mol, and its empirical formula is CHNO. What is its molecular formula? Show your work. C 8 H 10 N 4 O 2 1 mol C x g C = g C g x 1 formula = formula mol C mol g mol 1 mol H x 1.01 g H = 1.01 g H mol H 3(CHNO) = C 3 H 3 N 3 O 3 1 mol N x g N = g N mol N 1 mol O x g O = g O mol O g/formula II-2 Potassium oxide (K 2 O) is a major component of wood ash. When it is com-bined with water, it forms lye (potassium hydroxide, KOH). What is the theoretical yield of KOH if 150 g of K 2 O is combined with excess water? The balanced equation is shown below. Show your work. K 2 O + H 2 O 179 g KOH 2 KOH Molar mass of K 2 O = g/mol Molar mass of KOH = g/mol 150 g K 2 O x 1 mol K 2 O x 2 mol KOH x g KOH = 179 g KOH g K 2 O 1 mol K 2 O mol KOH

5 V-1 What is the molarity of a solution that contains 50.0 g of CaCl 2 in enough water to make 500 ml of solution? M 50.0 g CaCl 2 x 1 mol CaCl 2 = mol L sol'n g CaCl 2 L V ml of 1.50 M Ca(NO 3 ) 2 is diluted to 200 ml. What is the molar concentration of the dilute solution? CH0.488 mol/l 2 O M 1 V 1 = M 2 V 2 M 1 V 1 = V 2 V 2 = 1.50 M x 65.0 ml = M 200 ml V-3 Two solutions of CH 3 COOH are separated by a membrane that allows only water to pass through it. One of the solutions is 0.50 M and the other is M. After the liquids are allowed to equilibrate, which of the following conditions will be found? Check the correct answer. CH 3 COOH has flowed from the 0.50 M solution to the M solution. CH 3 COOH has flowed from the M solution to the 0.50 M solution. X Water has flowed from the M solution to the M solution. Water has flowed from the 0.50 M solution to the M solution.

6 VII-1 A container has a volume of 250 ml. What will the pressure of gas inside it be if there are moles of gas, and the temperature is 30 C? 45.7 atm P = X P x V = n x R x T = P = n x R x T V = L V n = mol P = mol x 303 K x L atm = 45.7 atm T = 30 C +273 = 303 K L mol K VII-2 Consider the following molecules, then answer the questions below. H H H C C H H H A. Ethane B. Ethanol 1. Give the name of the compound that will have the higher boiling point. Ethanol 2. What forces are present in that molecule but not present in the other one? Hydrogen bonds