Lab Exercise 7 to 11 Flashcards Preview

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Flashcards in Lab Exercise 7 to 11 Deck (22):
1

Which is false?
A.Groundwater dissolves the iron from soil and minerals. B.Iron also contributes to water hardness since it is a divalent ion.
C.Iron has harmful effects in humans.
D.Iron imparts a certain taste that will cause water rejection.

C

2

Which was not used @ Iron Det? For remaining, do sequence them :)
A. glass beads
B. NH4Ac buffer & phenanthroline
C. conc & hydroxylamine HCl
D. methyl orange

D. Orange shade kasi yung final color!! :))

C,A,B

3

Which forms red orange color @ Fe det?
A. NH4Ac buffer
B. Hydroxylamine hydrochloride
C. phenanthroline
D. methyl orange

C, upon rxn with Fe

4

Which is reducing agent @ Fe det?
A. NH4Ac buffer
B. Hydroxylamine hydrochloride
C. phenanthroline
D. methyl orange

B

5

@ iron det: NH4Ac buffer maintains pH @ __

3.5

6

False about chloride determination
A.via precipitation titration
B.excess AgNO3 is needed to react with K2CrO4
C.Colored precipitate happens before equivalence point
D.Reagent blank: ideally has no Ag

C - AFTER EQUIVALENCE
POINT
o At equivalence point, [Ag] = [Cl]
o Excess [Ag] is needed to form a precipitate with
chromate
o Thus the need for blank to measure the excess [Ag]

7

Which is false?
A. Cl standard for drinking H2O & irrigation H2O is the same
B. Chloride content increases as mineral content increases
C. Chloride has no significant health effects
D. Spray from ocean is carried inlands as droplets which constantly replenish the chloride content of inland waters

A
250 mg/L for drinking water
Less than 250 mg/L for water of irrigation

8

how can over pumping of groundwater increase Cl content

Overpumping of groundwater --> intrusion of seawater --> increase chloride content

9

identify determination method of:
A. chloride
B. sulfate

A. chloride - precipitation titration
B. sulfate - turbidimeter/colorimetric method

10

identify determination method of:
C. fluoride
D. iron

C. fluoride - colorimetric method
D. iron - colorimetric method

11

Not a conditioning reagent in sulfate determination
A.HCl
B.NaCl
C.BaCl2
D.glycerol

C

12

Which is not an effect of sulfate @ envi & health?
A.May hard scales in boilers & heat exchangers
B.Odor problems
C.Corrosion of sewers
D.Increase prevalence of NCDs
E.Acid rain

D

13

Iron, sulfate & fluoride determined via colorimetric method. What are their end colours, respectively?

iron - red orange
sulfate - blue
fluoride - red

14

Iron, sulfate & fluoride determined via colorimetric method. In what wavelengths are they read, respectively?

Fe - 510 nm
sulfate - 340 nm
F - 570 nm

15

respective standard values for:
A. fluoride
B. sulfate

A. 4 mg/L for drinking water
B. Less than or equal to 750 ppm. 250 mg/L for drinking water

16

What is chlorine demand & how is it determined?

 Amount of chlorine used up to oxidize substances in water
 Determined through iodometric method

17

reactions @ iodometric method - identify

Cl2 + 2I- --> I2 + 2Cl-
I2 + starch --> blue color

18

breakpoint chlorination denotes the ff except:
A.The point where the curve starts to rise again
B.The end of reaction of chlorine with impurities in water
C.the start of disinfecting ability of chlorine
D.NOTA

D

19

How is breakpoint chlorination determined?

iodometric method

20

What is residual chlorine?

Amount of chlorine remaining after some of the chlorine has reacted with substances in water

21

in residual chlorine, what was the titrant?

std. sodium thiosulfate solution (0.025 N)

22

Why do some samples have no breakpoint chlorination? enumerate two reasons

Some have no breakpoint chlorination maybe because:
o Breakpoint is found before the starting mL
o Water sample may contain different organic molecules
that react at different rates