Title: WQ section

Q: Which of the following half-reactions of persulfate is correct (under the conditions in experiment WQ11)?
- (S2O8)2- + 2e- --> 2 (SO4)2-
- (S2O8)2- + 2H+ --> (S2O7)2- + H2O
- (S2O8)2- + 2e- --> 2 (SO3)2- + O2
A: (S2O8)2- + 2e- --> 2 (SO4)2-

Q: Which type of phosphates can be quantified without digestive sample treatment?
- orthophosphates
- condensed phosphates
- organic phosphates
A: orthophosphates

Q: What is the oxidation state of tin in stannous chloride?
- +2
- +3
- +4
- +1
A: +2

Q: Which of the following hazards apply to concentrated ammonia solution (approx. 30 % in water)?
- toxic
- flammable
- carcinogenic (i.e, cancer-causing)
- corrosive
A: toxic; corrosive

Q: The pK_a of phenol is 10.0.  At pH 7.9, the majority of the phenol molecules are:
- protonated
- deprotonated
- positively charged
- negatively charged
A: protonated

Q: Which solution has the greater nominal ionic strength: 5 mol/L NaOH or 5 mol/L NH_4OH?
- Both have the same ionic strength.
- sodium hydroxide
- ammonium hydroxide
A: Both have the same ionic strength.

Q: What is the approximate temperature of the flame in an AAS instrument?
- 400-500 K
- 900-1150 K
- 2000-3000 K
- 3600-4000 K
A: 2000-3000 K

Q: What is the electron configuration of cadmium?
- [Kr] 4d10 5s2
- [Ar] 3d10 4s2
- [Kr] 5s2
A: [Kr] 4d10 5s2

Q: The solution used to spike the shell sample in the standard addition method contains which acid?
- sulfuric acid
- nitric acid
- hydrochloric acid
A: sulfuric acid

Q: What is the boiling point of phenol?
A: 182 (± 3)

Q: Which hazards are associated with concentrated nitric acid?
- Oxidising agent
- Corrosive
- explosive
- flammable
A: Oxidising agent; Corrosive

Q: What indicates the endpoint of the titrations in WQ1?
- The gradient of potential change vs added volume reaches a maximum
- The gradient of potential change vs added volume reaches a minimum.
- A precipitate forms.
- The colour of the solution changes from white to dark purple.
A: The gradient of potential change vs added volume reaches a maximum

Q: Which of the following statements is correct?
- When reading the titre off a burette, the eyes should be at the same level as the meniscus of the liquid.
- When refilling a burette, the eyes should be at the same level as the the zero mark on the burette.
- Burettes should be cleaned by rinsing them under the tap.
A: When reading the titre off a burette, the eyes should be at the same level as the meniscus of the liquid.

Q: Under what condition does Zobell's solution release hydrogen cyanide gas?
- Acidic conditions
- Oxidative conditions
- Alkaline conditions
- Reductive conditions
A: Acidic conditions

Q: Besides being highly toxic, sodium azide can combine with heavy metals, such as copper or lead, to form metal azides. What particular hazard do metal azides pose?
- They are explosive.
- They are carcinogenic.
- They are highly corrosive.
A: They are explosive.

Q: What should be the concentration ratio of the supporting electrolyte and the analyte in electrochemical measurements?
- The electrolyte concentration should be much greater than the analyte concentration.
- The analyte concentration should be much greater than the electrolyte concentration.
- Both concentrations should be approximately the same.
- Depends on the type of electrochemical cell.
A: The electrolyte concentration should be much greater than the analyte concentration.

Q: What is the formal oxidation state of the sulfur atoms in the tetrathionate ion (S_4O_6^2-)?
- +2.5 for all sulfur atoms
- +2 and +3 for two sulfur atoms each
- Zero and +5 for two sulfur atoms each
- +3 for all sulfur atoms
- +4 and -2 for two sulfur atoms each
A: Zero and +5 for two sulfur atoms each

Q: What is the dilution factor between standard 1 and standard 5 in the preparation of fluoride standards in this experiment?
A: 10000