Chemistry 1411 Sample EXAM # 2 Chapters 4, & 5 Activity Series of Metals in Aqueous Solution 1
CHEM 1411 Exam # 2 (Chapters 4, & 5) Part I- Please write your correct answer next to each question number. 1. Which of the following are nonelectrolytes in water? (i) HF (ii) ethanol, C 2 H 5 OH (iii) CH 3 OCH 3 (iv) KClO 3 A. ii and iii B. i, ii, and iii C. iii only D. ii only 2. How many milliliters of 1.50 M KOH solution are needed to supply 0.125 mole of KOH? A. 0.0833 ml B. 0.188 ml C. 12.0 ml D. 83.3 ml 3. Which of the following is/are soluble in water? (i) NiCl 2 (ii) Ag 2 S (iii) Cs 3 PO 4 (iv) (NH 4 ) 2 SO 4 A. iv only B. i, ii, and iii C. i, ii, and iv D. i, iii and iv 4. Which of the following reactions will occur? (i)ni(s) + Zn 2+ (aq) (iii)zn(s) + Ca 2+ (aq) (ii)pb(s) + Ag + (aq) (iv)al(s) + Fe 2+ (aq) A. i only B. ii only C. ii and iv only D. i and iii only 5. Which of the following is a weak base? A. NaOH B. Ca(OH) 2 C. NH 4 OH D. RbOH 6. Which of the following gas has higher density at STP condition? A. CH 4 B. Cl 2 C. CO 2 D. O 2 7. How many moles of N 2 gas occupy 11.2 liters volume a STP condition? A. 1.0 mol B. 2.0 mol C. 0.50 mol D. cannot be determine 8. Which of the following is/are not characteristic of gases? I. high density II. formation of homogeneous mixtures III. low intermolecular forces A. I only B. I and III C. I, II, and III D. II and III 9. An unknown gas " X " effuses two times faster than a sample of SO 3(g) through a porous container. Which of the following is the unknown gas? A. H 2 B. CH 4 C. Ne D. Ar 2
10. Which of the following is not a statement of Boyle's law? All statements assume constant temperature and amount of gas. A. P = constant/v B. V α 1/P C. P/V = constant D. PV = constant 11. All of the following are weak acids except A. HCNO B. HBr C. HF D. HNO 2 E. HCN 12. How many grams of NaCl are contained in 350.ml of a 0.250 M solution of sodium chloride? A. 41.7g B. 5.12g C. 14.6g D. 87.5g E. None of these 13. Consider the reaction; Zn + H 2 SO 4 ZnSO 4 + H 2. Which element (if any) is oxidized? A. zinc B. hydrogen C. sulfur D. oxygen E. None of these 14. In which of the following does nitrogen have an oxidation state of +4? A. HNO 3 B. NO 2 C. N 2 O D. NH 4 Cl E. NaNO 2 15. In the balanced molecular equation for the neutralization of sodium hydroxide with sulfuric acid, the products are: A. NaSO 4 + H 2 O B. NaSO 3 + 2H 2 O C. 2NaSO 4 + H 2 O D. Na 2 +2 H 2 O E. Na 2 SO 4 + 2H 2 O 16. What volume of 18.0 M sulfuric acid must be used to prepare15.5l of 0.195 M H 2 SO 4? A. 168 ml B. 0.336L C. 92.3 ml D. 226 ml E. None of these 17. What volume is occupied by 19.6 g of methane ( CH 4 ) at 27 o C and 1.59 atm? A. 1.71 L B. 18.9L C. 27.7 L D. 302 L E. Not enough data to calculate 18. Which gas has the highest density? A. He B. Cl 2 C. CH 4 D. NH 3 E. All gases the same. 19. The mass of 1.12 liters of gas Y is found to be 6.23g. The density of gas Y is: A. 10.6 g/l B. 5.56 g/l C. 15.6 g/l D. 0.200 g/l E. 0.180 g/l 20. The density of Nitrogen at STP is: A. 1.60 g/l B. 0.800 g/l C. 1.25 g/l D. 0.625 g/l E. Not enough information 21. Order the following in increasing rate of effusion: F 2, Cl 2, NO, NO 2, CH 4 A. Cl 2 < NO 2 < F 2 < NO < CH 4 B. Cl 2 < F 2 < NO 2 < CH 4 < NO C. CH 4 < NO 2 < NO < F 2 < Cl 2 D. CH 4 < NO < F 2 < NO 2 < Cl 2 3
E. F 2 < NO < Cl 2 < NO 2 < CH 4 PART II- ( 5 points each) Please show all your work. 1. Write a complete ionic and net-ionic equation for the following reaction. K 2 CO 3 (aq) + H 2 SO 4 (aq) 2. a) What volume(ml) of 0.115 M HClO 4 solution is required to neutralize 50.00 ml of 0.0875 M Ca(OH) 2? b) A solution contains 3.2 g NaOH ( MW = 40) in 20.0 ml of solution. What is the molarity of the solution? 3. 2.50 g CO 2 gas occupies 5.60 liters at 789 torr. a) Calculate the temperature of gas in 0 C. b) What is the density of CO 2 gas at STP condition? 4. What volume of O 2 (g), measured at 22 C and 763 torr, is consumed in the combustion of 7.50 L of C 2 H 6 (g), measured at STP? 2 C 2 H 6 (g) + 7 O 2 (g) 4 CO 2 (g) + 6 H 2 O(l) 5. A 1200 ml sample of helium gas is at a pressure of 350 mmhg and a temperature of 300 K. What volume will this gas sample occupy if the pressure is increased to 700 mmhg and the temperature is increased to 400 K? 6. A sample of gas has a mass of 0.311 g. Its volume is 0.225 L at a temperature of 55.0 C and a pressure of 886 mmhg. Find its molar mass. 7. A gaseous mixture containing 1.5 mol Ar and 3.5 mol CO2 has a total pressure of 7.0 atm. What is the partial pressure of each gas? 4
1411 SAMPLE EXAM # 2 (Key) PART I 1. A 2. D n = M.V L V L = (n /M) = (0.125 mol/ 1.50 mol/l) = 0.0833 L x 1000 = 83.3 ml 3. D 4. C 5. C 6. B Cl 2 has highest molecular weight = 71.0 gr/mol 7. C (11.2 L) ( 1 mol / 22.4 L) = 0.50 mol N 2 8. A 9. C rate(x) / rate (SO 3 ) = ( M SO3 /M x ) ½ 2 = ( 80 / M x ) ½ 4 = 80 / M x M x = 80/4 = 20 Neon 10. C 11. B 12. B g (NaCl) = M. V.MW = (0.250 mol/l)(0.350 L)(58.5 g/mol) = 5.12 g, NaCl 13. A 14. B 15. E 16. A M 1 V 1 = M 2 V 2 V 1 = ( 0.195)(15.5)/(18.0) V 1 = 0.168 L x 1000 ml/l = 168 ml 17. B PV = nrt = (mrt/m) V = (mrt/mp) = (19.6g)(0.0821 L.atm/mol.K)(300 K)/ (16 g/mol)(1.59 atm) = 18.9 L 18. B ( Cl2 = 71 g/mol, highest molecular weight) 19. B D = m /V = (6.23 g) / 1.12 L = 5.56 g/l 20. C g (N 2 at STP) = ( M/22.4) = ( 28 g /mol) / (22.4 L/mol) = 1.25 g /L 21. D PART - II 1. molecular equation: K 2 CO 3 (aq) + H 2 SO 4 (aq) K 2 SO 4 (aq) + H 2 CO 3 (aq) ioninc equation : 2K + (aq) +CO 3 2- (aq)+ 2H + (aq) +SO 4 2- (aq) 2K + (aq) + SO 4 2- (aq) + H 2 O(l) +CO 2 (g) net-ionic equation : 2H + (aq) + CO 3 2- (aq) H 2 O(l) +CO 2 (g) spectator ions : 2 K + and SO 4 2-5
n b M b V b (2)(50.00)(0.0875) 2. a) V a = ----------------- = --------------------------------- = 76.1 ml n a M a (0.115) (3.2/40 mole) b) M = ----------------------- = 4 mol/ L ( mol.l -1 ) or molar (20.0/1000 L) 3. a) PV = nr T PV = (m/m) RT T = ( MPV/m R) = (44)(789)(5.60)/(760)(2.50)(0.0821) =1246 K = 973 o C 102 K b) D(CO 2 ) STP = (M /22.4) = 44/22.4 = 1.96 g/l 4. (7.50 L C 2 H 6 )( 1mol C 2 H 6 / 22.4 L) ( 7 mol O 2 / 2 mol C 2 H 6 ) = 1.17 mol. O 2 V = ( nrt/p) = (1.17)(0.0821)(273+22)(760)/(763) = 28.2 L 5. P 1 V 1 /T 1 = P 2 V 2 /T 2 ; V 2 = (P 1 V 1 /T 1 ) x (T 2 /P 2 ); V 2 = ((350 x 1200 )/ (27 + 273)) x (400 /700); V 2 = 800 ml 6. n = 9.7454 x 10-3 mol Molar mass = 31.9 g/mol 7. Pco 2 = nco 2 / nt x Pt = 3.5/5.0 x 7.0 = 4.9 atm P Ar = n Ar /nt x Pt = 1.5/5.0 x 7.0 = 2.1 atm 6