Salt Analysis & Ion Selective Electrodes

Question 1

Precipitation
Titration

Answer 1

At least one product of a titration reaction is
an insoluble precipitate

Question 2

Mohr method

Answer 2

NaCl estimated by titrating the Cl ion w/ silver

Formation of orange color when silver reacts w/ chromate

pH 6.5-9

Question 3

Mohr method
interference

Answer 3

Br and other (-) ions can interfere

Question 4

Volhard method

Answer 4

Indirect back titration
Precipitate chlorides w/ excess silver
Excess silver titrated w/ potassium thiocyanate
Use Fe cations to detect endpoint

Acidic pH

Question 5

Volhard cons

Answer 5

Need a blank

Can’t use for red foods

Question 6

Chloride analyzer

Answer 6

Based on colormetric titration

End point when excess silver ions cause change in conductivity

Sense w/ electrodes

Question 7

Chloride analyzer pros

Answer 7

Not super expensive

Don’t have to worry about end point visually

Easy to use

Question 8

Chloride analyzer cons

Answer 8

Have to buy buffer and parts

Question 9

Ion selective electrode

Answer 9

Measurement of specific ions

Wide variety of applications

Question 10

Applications of ISE

Answer 10

Salt in processed meats
Ca in milk
Na in low salt products
K in fruit juices

Question 11

ISE advantages

Answer 11

Measures anions and cations directly
Simple
Independent of of volume
Turbidity, color, viscosity = not a concern

Question 12

ISE disadvantages

Answer 12

Can’t measure super low concentrations
Slow response time for low-concentration
Short operating life
Cost

Question 13

Test strips

Answer 13

Placed in aq solutions
Fluids rise up strip
Strip contains silver

Question 14

Test strip pros

Answer 14

Built in scale
Cheap
Easy

Question 15

Test strip cons

Answer 15

Semi quantitative
Accurate +/- 10%