16-exam3

16-exam3 - CHEMISTRY 16 EXAM III-Version 1 Dr. M....

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CHEMISTRY 16 EXAM III-Version 1 Dr. M. Richards-Babb July 23, 1998 An optical scoring machine will grade this examination. The machine is not programmed to accept the correct one of two sensed answers and will not sense answers which are lightly marked. Mark your answer sheet carefully with a No. 2 soft lead pencil and erase any undesired marks COMPLETELY. Avoid making any extraneous marks on the answer sheet other than the information requested below. On the answer sheet: 1. Print your name in the space for NAME (last name first, circle your last name). 2. In the space marked SUBJECT print your student number. 3. In the space marked HOUR print Summer II ‘98. Check to see that you have 20 examination questions, periodic table and scratch paper when the exam begins. HAND IN ONLY THE ANSWER SHEET. Useful Equations and Constants: Kw_=l.0x10"“ at 25°C x = [-b :I: (b2 — 4ac)"‘] / 2a CHEMISTRY 16 HOUR EXAM III CHOOSE THE ONE BEST ANSWER. Summer 1998 J}. The pH of 0.075 M HOBr is: (KA(HOBr) =' 2.06X10‘9) xix. A. 4.91 . 7.50 ‘ C. 4.15 D. 9.09 E. A 1.24 Calculate KB for the Conjugate base of formic acid HCOOH. (KA(HCOOH) = 1.77x10“) A. - 5.6x10'” B. l.8><10'° C. 5.6><IO‘3 D. l.8><lO'18 E. 3.l><10'8 Strychnine is a weak base with K3=1.6x10‘5. The equilibrium for KB can be represented as below (where B stands for neutral molecules of strychnine). 'flie Concentration of OH‘ in 0.090 M strychnine is: B(aq) + H20 H BH+(aq) + 0H'(aq) KB=1 .6X 10* 2.4><1o-ll M - 9.0><10-'2 M 1.4x10-7 M 3.8x104M ~ 0.090 M F1509"? 4mm..- . The pH of 0.025 M NaOCl is: (KA(HOC1) = 2.95x10") IA. 3.00 B. 8.46 C. 9.47 D. 12.40 E. 5.49 Which of the salts below will give an acidic solution when dissolved in water? Al(N03)3 KC2H302 NaNo3 NH4Br A. All will give an acidic solution. B. NaNO3, Al(NO,)3 and NH4Br C. Al(NO,)3 and NH4Br D. KCZH302 E. NH4Br The pH of a bufier that contains 0.100 M HC3H502 (propionic acid) and 0.400 M KCJHSOZ (potassium propionate) is: (KA(HC3H502)=1 .34x 10.5) A. 2.94 9 B. 9.56 C. 4.21 D. 5.47 E. 4.87 Which of the following systems constitutes a buffer when l L of each solution is mixed? A. 0.2 M HC1/0.1 M NaOH B. 0.1 M KOH/0.5 M KCl C. 0.5 M MILO/0.2M HCl D. 0.5 M 181114025 M NaOH E. 0.5 M NH3/O.25 M HCl When KOH is added to a HNO/NaNOz buffer system, the OH' will react ‘ with the A. _ 100% ; HNO, B. incompletely; Na” C. 100%; N02' D. 50%; H20 E. incompletely; HN02 Jo. 11. Hydroxylamine (NHZOH) is a weak base. The equilibrium established by NHZOH in water is shown below. NHZOH + H20 H NH3OH+ + OH‘ As solid NaNH3OH is added the [OH‘] while the pH - ' decreases; increases increases; increases increases; decreases decreases; decreases remains the same;-remains the same €11,009”? A pH buffered at 4.00 is needed to standardize a pH meter. A buffer system made out of which of the following acids will work best? Acrylic acid (KA=5.6X10'5)' Barbituric acid (KA=9.8><10'5) Oxalic acid (KA=5.9><10'2) Uric acid (KA=1.3><10") Arsenious acid (KA=6><10"°) mpow> A 15.0 mL sample of 0.15 M NH; is to be titrated with 0.25 M HCl. The volume of HCl needed to reach the equivalence point will be and the pH at the equivalence point will be - A. 5.6 mL; neutral B. 2.5 mL; basic C. 9.0 mL; acidic D. 17 mL; acidic E. 9.0 mL; basic A 20. mL sample of 0.10 M HCl is to be titrated with 0.20 M NaOH. What will be the pH of the solution after the addition of 7.5 mL of NaOH? ' A. 1.00 B. 12.19 C. 1.74 D. 6.21 E. 7.00 13. A 10. mL ‘sample of 0.10 M uric acid (a weak acid KA=1.3><10“‘) is titrated with 0.20 M . NaOH. If 5.0 mL of NaOH are needed to reach the equivalencepoint, what is the pH of the solution half-way to the equivalence point (after addition of 2.5 mL of NaOH)? A. 10.00 B. 5.35 C. 8.71 D. 3.89 E 4.57 ‘114. Which of the ions below will react with water (hydrolyze) to give either an acidic or basic solution? ' K+ Br“ NO; C10; . F' @909”? 15. Which of the following statements is TRUE about buffers? A. A buffer works best when the concentration of acid and base are nearly equal. B. Dilution alters the pH of a buffer. C. Addition of a small amount of strong acid to a buffer solution causes a sharp decrease in the pH of the buffer solution. D. The pH of a buffer solution is always equal to pKA independent of the concentrations of weak acid and conjugate base present. E. Addition of a small amount of strong base to a buffer solution causes a sharp increase in the pH of the buffer solution. ' 16. Whichof the following statements is TRUE about the indicator methyl red (KA‘,n=5X10")? (HINT: Calculate pKMn) Methyl red is a basic indicator. Methyl red can be used to accurately determine the end point for any titration. Methyl red changes color at pH=7.00. Methyl red can be used to determine the end point when titrating a weak base with a strong acid. Methyl red has the same color in both acidic and basic solutions. $7.09”? 1'” 17. The molar solubility of BaSO4 in water is: K,p(BaSO4)=1.0><10"° A. 3.2><10'3 M B. 5.3X10" M A C. 1.0X10'5 M D. 6.7><10'4 M E. 2.3><10‘3 M 18. The concentration of Hg“? in a saturated solution of HgI2 is 1.93X10"° M. The numerical value of Ksp for Hglz is: A. 7.28X10‘3" B. 2.88><1'0'29 C. 7.72X10‘lo g D. 5.53X10'ls E. 3.72X10'20 . 19. Which condition characterizes the equivalence point in the titration of an acid with a base? A. Stoichiometric amounts of acid and base have‘reacted. B. A slight excess of titrant is present. C. The point where the indicator changes color.- D. The pH is exactly 7.0. E. The pH remains constant with addition of excess base. 20. Which one of the following sulfides is LEAST soluble in water (ie. has the lowest molar solubility)? Ks» A. FeS 6.3x10‘” B. MnS 2.5><10'l3 ‘ C. NiS * 1.0x10'2‘ D. CdS 8.0><10‘27 E. HgS 1.6><10"2 ...
View Full Document

This note was uploaded on 04/26/2008 for the course CHEM 116 taught by Professor Chigwada during the Summer '07 term at WVU.

Page1 / 6

16-exam3 - CHEMISTRY 16 EXAM III-Version 1 Dr. M....

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online