LAB 4

Question 1

chemical reactions can be described as

Answer 1

• precipitation reactions
• acid-base reactions
• redox reactions

Question 2

What are we trying to determine

Answer 2

The amount Mg(OH)2 in a sample of Milk of Magnesia

Question 3

What is Milk of Magnesia

Answer 3

magnesium hydroxide: strong but only slightly soluble base
It works as an antacid that neutralizes excess H+ in stomach acid by providing it with OH- ions

Question 4

What percent of Mg(OH)2 should milk of magnesia contain

Answer 4

around 7%

Question 5

What makes titration difficult with Milk of Magnesia

Answer 5

Cloudy suspension, some material may cling to the sides of the flash preventing complete titration and lowering apparent amount of Mg(OH)2

Question 6

How can we prevent titration issues with Milk of Magnesia

Answer 6

Ensuring extra HCl (acid) is added to react with suspended Mg(OH)2 (BACK TITRATION APPROACH) resulting in a clear solution

Question 7

What do we do with the excess (un-reacted) acid

Answer 7

titrated with NaOH

Question 8

What is KHP

Answer 8

Potassium Hydrogen Phthalate

Question 9

What is standardization

Answer 9

method to accurately determine the concentration of a solution, for ex. using titration

Question 10

What is titration

Answer 10

exact volume and known concentration of a titrant is used to completely react with a specific volume of an analyte of unknown concentration

Question 11

What is a good primary standard

Answer 11

a reagent that is extremely pure, stable, has no water of hydration, and a high molecular weight
KHP will be our primary standard

Question 12

Equivalence point

Answer 12

When moles of acid and base are equal in solution

Question 13

Indicator

Answer 13

identify the equivalence point
- phenolphthalein (pink)

Question 14

What is our standardized solution

Answer 14

NaOH