EDTA

Question 1

water hardness

Answer 1

amount of calcium and magnesium contained in water

Question 2

low concentration of ions

Answer 2

soft water (corrosive)

Question 3

high concentration of ions

Answer 3

hard water (hard water scales)

Question 4

Mg and Ca in natural waters do what

Answer 4

regulate pH and reduces toxicity of metals that enter the water

Question 5

ligand

Answer 5

a species that is an electron donor and binds to a metal (electron acceptor)

Question 6

Ligands in EDTA

Answer 6

lone pairs on N and O

Question 7

Metal-ligand complex

Answer 7

metal surrounded by the ligand of a compound

Question 8

How must EDTA titrations occur?

Answer 8

in basic conditions

Question 9

Each molecule of EDTA

Answer 9

binds to one metal ion

Question 10

Indictors

Answer 10

organic dyes that form stable complexes with metal ions

Question 11

What is special about these indicators?

Answer 11

their colour depends on the presence of free metal ions

Question 12

Before titration

Answer 12

indicator will bind to the metal ions in solution (formation of EDTA)

Question 13

During titration

Answer 13

EDTA reacts with free metal ions.

Question 14

Nearing endpoint and after

Answer 14

EDTA release the metal ions from the INDICATOR to form metal-EDTA complexes

Question 15

indicators used in experiment

Answer 15

calcon and hydroxynaphthol blue

Question 16

what colour are the solutions at the beginning of titration?

Answer 16

red-pink

Question 17

what colour are the solutions at the end of titration?

Answer 17

blue

Question 18

what colour are the solutions at during titration?

Answer 18

purple

Question 19

Why is a pH 10 buffer solution needed?

Answer 19

1. EDTA needs to exist in its deprotonated form
2. controls the binding strength of the indicator molecules to the metal ions

Question 20

Why is NaOH needed?

Answer 20

To precipitate MgOH, leaving CaOH as the remaining molecule to titrate.

Question 21

Total concentration of Ca and Mg ions

Answer 21

CtitrantVtitrant=CanalyteVanalyte

Question 22

Binding affinity

Answer 22

a measure of how well two compounds bind together

Question 23

How do you know which one has more binding affinity?

Answer 23

The molecule affected by the basic state will have a lower binding affinity than the other molecule

Question 24

Common products EDTA is used in

Answer 24

Skin Care, Laundry Detergent

Question 25

If a question asks to convert the waterhardness to mg/L

Answer 25

convert both Mg and Ca seperately and then combine together