The following practice examination contains 40 questions. The final will contain 38 questions valued at 3 points/question. 1 d

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1 Chem Final Exam Practice Spring 8 The following practice examination contains 4 questions. The final will contain 38 questions value at 3 points/question. Name KEY % w/v = (g solute/ml solution) M V = M V %C V = %C V T f = -(.86 o C/mole)(moles) T b = (.5 o C/mole)(moles).86/.5 = MW/x % w/v = (g solute/ml solution) ph = -log[h + ] poh = -log[oh - ] ph + poh = 4[A - ]/[AH] = ph pka or log ([A - ]/[AH]) = ph - pk a M AV A = M BV BN = N o(/) n or. How much NaCl is require to make 5. ml of 3. M NaCl? a..9 g b g c. 6.3 g g e..7 x 3 g.5 L(3. mol/l)(58.4 g/mol) = 6.3 g. What volume of 3. M NaCl is require to make 45. ml of. M NaCl? a. 5. x ml b.. x ml c..5 x ml. 3. x ml e x ml M V = M V (3. M)V =. M(45. ml)

2 Acetic aci (MW = 6. g/mol) is such a weak aci (Ka =.8 x -5 ) it can essentially be treate as non-issociating for the purposes of the following 4 questions. 3. What is the freezing point of.8 x g acetic aci issolve into. L water? a. 3 o C b o C c o C. -.9 o C e. -.6 o C.8 x g(mol/6. g) = 3. mol T f = -(.86 o C/mole)(moles) = -(.86 o C/mole)(3. mol) = -5.6 o C The new freezing point is the same as the change in freezing point since water freezes at. o C. T f = T f - T i = -5.6 o C = T f. o C 4. What is the boiling point of.8 x g acetic aci issolve into. L water? a..6 o C b. 3 o C c..6 o C. 5.6 o C e. 3 o C.8 x g(mol/6. g) = 3. mol T b = (.5 o C/mole)(moles) = (.5 o C/mole)(3. mol) =.6 o C Now that we have the change in boiling point we can fin the new boiling point T b =.6 o C = T f - T i = T f o C 5. How much acetic aci woul have to be ae to. L of water to make an isotonic solution? a..7 g b..9 g c. 6. g. 7 g e. 6. x g.86/.5 = MW/x or x = MW(.5/.86) = 6.(.5/.86) = 7 g

3 mole of anything will lower the freezing point of water by.86 o C. Since all the stuff in boily fluis combine lowers the freezing point by only.5 o C, we only nee the.5/.86 fraction of a mol to make the solution isotonic, so multiply this fraction by the molar mass of the compoun in question (for. L of isotonic solution) 6. What is the w/v % of an isotonic acetic aci solution? a..7 % b..9 % c. 6. %. 7 % e. 6. x % 7 g/l =.7 g/l Bonus (3 EC): The Unite States Foo & Drug Aministration requires vinegar to be at least 4. % w/v acetic aci. s vinegar hypotonic, isotonic, or hypertonic? a. Hypotonic b. sotonic c. Hypertonic 7. What is the efinition of a base? a. ph < 7 b. ph > 7 c. A proton onor. A proton acceptor () is the funamental efinition of a base. ph quantifies how aciic or basic an aqueous solution is. Bases generate hyroxie (OH - ) in solution giving rise to ph values > 7 8. What is the ph of a solution in which 3.65 mg HCl is issolve in. L HO? a.. b.. c e. 3 MW HNO 3 = 36.5 g/mol (3.65 x -3 g)(mol/36.5 g) =. x -4 mol. x -4 mol /. L. x -4 M ph = 4

4 9. What is the ph of a solution in which 4 g NaOH is issolve in, L HO? a. b. 3 c.. e. MW NaOH = 4. (4 g)(mol/4. g) = mol mol/, L =. x -3 M poh = 3 ph + poh = 4 ph + 3 = 4 Remember, bases ae to water will always prouce a ph > 7. Which of the following compouns will lower the ph of HO? a. HCl b. HNO 3 c. H SO 4. None of the above e. All of the above All of the above are strong acis. Which of the following compouns will raise the ph of HO? a. NaCl b. NaNO 3 c. NaHSO 4. None of the above e. All of the above The conjugate bases of strong acis are so weak they are essentially non-bases an only make the water salty they o not influence the ph. Which of the following compouns will lower the ph of HO? a. CH 3 CO H b. CH 3CH OH c. CH 3NH. (a) an (b) e. All of the above Be on the lookout for the RCO H motif these are the carboxylic acis, very important weak acis in organic chemistry

5 3. Which of the following compouns will raise the ph of HO? a. CH 3CO H b. CH 3CH OH c. CH 3 NH. (a) an (b) e. All of the above Be on the lookout for the RNH motif these are the amines, very important weak base analogs of ammonia in organic chemistry 4. n the aci-base reaction below, inicate the conjugate base of the aci an the conjugate aci of the base by rawing a line between them an labeling. Label both members of each pair. Base C.A. 3HCl + Al(OH)3 AlCl3 + 3HO Aci C.B. 5. n the aci-base reaction below, inicate the conjugate base of the aci an the conjugate aci of the base by rawing a line between them an labeling. Label both members of each pair. Aci C.B. NH4Cl + NaOH NaCl + NH3 + HO Base C.A. 6. n the aci-base reaction below, inicate the conjugate base of the aci an the conjugate aci of the base by rawing a line between them an labeling. Label both members of each pair. Aci C.B. HCO3 + NH3 NH4HCO3 Base C.A. 7. Which of the following is the strongest base? a. Na 3 PO 4 b. Na HPO 4 c. NaH PO 4. H 3PO 4 e. All are equally strong bases Each time you remove a proton from a polyprotic aci you buil up more charge on the polyatomic ion/conjugate base, thus estabilizing it

6 8. Please give the proucts of the following aci-base reaction as written. f there HNO3 + NH3 NH4NO3 9. Please give the proucts of the following aci-base reaction as written. f there HNO3 + NH4Cl NR With NH 4Cl being the [weak] conjugate aci of a weak base, both are acis. Please give the proucts of the following aci-base reaction as written. f there H3PO4 + 3NaOH Na3PO4 + 3HO. Please give the proucts of the following aci-base reaction as written. f there CH3COH + CH3NH CH3CO - + CH3NH3 + Reaction between a weak aci an weak base. Please give the proucts of the following aci-base reaction as written. f there NaSO4 + HCl NaHSO4 + NaCl Tough one H SO 4 is a very strong aci giving rise to HSO 4 -. HSO 4 - is still aciic, but since it alreay bears a - charge, losing another H + is more ifficult. As a result, the available proton on HCl woul rather hang with SO 4 - than Cl - 3. What is the ph of a buffer system containing carbonic aci (H CO 3, pk a = 6.4) at a concentration of. mm an soium bicarbonate (NaHCO 3) at a concentration of. mm? a. 4.4 b. 5.4 c e. 8.4 H CO 3 = AH HCO 3 - = A - [A - ]/[AH] = ph pka. mm/. mm = = ph 6.4 = ph 6.4 x higher basic component rives ph units higher (in the more basic irection)

7 4. What is the ph of an unknown NaOH solution if a. ml sample requires 4. ml of.5 M HCl to reach the equivalence point? Please show your work. M AV A = M BV B (.5 M(4. ml) = (M B)(. ml) M B = (.5 M)(4. ml/. ml) =. M =. x - M poh = ph + poh = 4 ph + = 4 Answer: ph = 3 5. How many neutrons are in 9 Sr? a. 9 b. 5 c e. Cannot be etermine from the information given 9 38 = 5 6. Which of the following is the nuclear symbol for the positron? 4 a. He b. c.. e. e H n e 7. When a positron is emitte from the nucleus of a raionuclie, which of the following is also occurring in the nucleus? a. A proton is being converte into a neutron b. A neutron is being converte into a proton c. An electron is being converte into a proton. An electron is being converte into a neutron e. Gamma raiation is being converte into an electron The whole point of ejecting a positron is to rise the neutron to proton ratio by keeping the [neutron] mass an spitting out the [proton] charge (of course an outer electron then has to leave the new atom to maintain charge neutrality)

8 8. Please complete the following nuclear reaction 35 S? + e? = Chlorine Please complete the following nuclear reaction C B +?? = + or positron or e 3. Please complete the following nuclear reaction 38 4 Pu He +?? = Uranium Please complete the following nuclear reaction? = Hyrogen-3 (tritium) or 3? He e 3 H 3. Please complete the following nuclear reaction? = Neon-4 4? Na e 33. Please complete the following nuclear reaction? + n 98 Au H 98? = Mercury-98 or Hg 34. Technetium-99m is a very useful raionuclie for iagnostic imaging. One of its avantages is its short t/ of 6. hr an it can be mae conveniently on site. f a mci ose of Technetium-99m for a bone scan is not use for. ay, what is the remaining raiation intensity? 4 hr(t //6. hr) = 4 t / After half-life mci ng, after half-lives 5. mci After 3 half-life.5 mci ng, after 4 half-lives. mci Alternatively, use N = N o(/) n N = mci(.5) 4 =. mci Answer:. mci 35. f the mci ose of Technetium-99m for a bone scan is not use for 5 hr, what is the remaining raiation intensity? Here you have to use N = N o(/) n 5 hr(t //6. hr) =.5 t / N = mci(.5).5 = 3.5 mci Makes sense half-life gives 5. mci an 3 gives.5 mci Answer: 3.5 mci ntereste iniviuals will want to search moly cow

9 36. f the intensity of mci is measure. cm from the Technetium-99m, what is the intensity. m away where a clinician is staning? Use or = mci(. cm/ cm) = mci(. cm / x 4 cm ) =. mci Answer: Ci Don t like being irraiate? Just get away from source since intensity ecreases exponentially with istance 37. Which of the following raioactive particles has the most limite penetrating capacity? a. b. c.. e. 4 He e H n e 38. Which of the following is a measure of raiation intensity? a. Curie b. Roentgen c. Ra. Rem 39. Which of the following is a measure of raiation ose absorbe? a. Curie b. Roentgen c. Ra. Rem 4. Which of the following is a measure of raiation elivere? a. Curie b. Roentgen c. Ra. Rem