Experiment C: Stoichiometry And Reactions In Aqueous Solutions

Question 1

What are the two objectives

Answer 1

1) chemical reactions are used to transform scrap aluminum to alum

2) mass percent of phosphorus in fertilizer sample will be determined

Question 2

What are the two parts of the experiment

(Have to say chemical formula for alum in first part)

Answer 2

1) formation of KAI(SO4)2•12H2O from aluminum scraps

2) phosphorus in fertilizer

Question 3

What is the most abundant metal and 3rd most abundant metal in earths crust

Answer 3

Aluminum

Question 4

What element is wildest distributed in alumino-silicate minerals and clays

Answer 4

Aluminum

Question 5

What is the main ore of aluminum

And what is it a mixtures of, need to say chemical formula

Answer 5

Bauxite

A hydrate of aluminum oxide, Al2O3, mixed with oxides of iron, silicon, and titanium

Question 6

Why was aluminum expensive to produce

Until the development of what process

Answer 6

Due to the stability of Al2O3

Until Hall-Hercult process

Question 7

Aluminum production requires ____ of energy

Melting point of Al?

Answer 7

A lot

660 degrees

Question 8

Chemical formula for Alum

Correct chemical name

And two other names it can be called

Answer 8

KAI(SO4)2•12H20

Aluminum sulfate dodecahydrate

Also called potassium alum or kalinite

Question 9

Steps for alum part of experiment with chem formulas

(3)

Answer 9

1) scraps will be dissolved by a reaction with hot potassium hydroxide, KOH using a hot plate

Al(s) + KOH (aq) + H20 —> K+(aq) + Al(OH4)4- + H2(g)

2) sulfuric acid, H2SO4 is added and initially a white solid forms, when heated again,
Al(OH)3 (s)

Al(OH4)- (aq) + H2SO4 (aq) —> Al(OH3) (s) + H20 + SO4 2- (aq)

3) Al(OH3) (s) undergoes further reaction

Al(OH)3 (s) + H2SO4 (aq) —>
Al3+ (aq) + SO4 2- (aq) + H2O

Solution left in locker to form crystals of alum

Question 10

In the steps for alum production, which compound is amphoteric

What does amphoteric mean

Answer 10

Al(OH)3 (s)

Can react with either acid or base

Question 11

What does the label on the fertilizer show

Ex) 10-20-10

Have to say chemical formula

Answer 11

1) guaranteed mass percent of total nitrogen

2) available phosphoric acid, H3PO4

3) soluble potash, K2O

Question 12

What is the “mass percent” of a solution

Answer 12

The RATIO of the mass of SOLUTE that is present in a solution, RELATIVE, to the MASS of the solution as a whole

Question 13

What compound is not actually in fertilizer, and what is the usual compound

Have to say chemical formulas

Answer 13

P205, diphosphorus pentoxide

Usual: (NH4)H2PO4, ammonium dihydrogen phosphate

Question 14

Steps for part 2 of experiment, mass percent of phosphoric acid (3)

Answer 14

1) known mass of fertilizer will be mixed with water to dissolve the
(NH4)H2PO4, ammonium dihydrogen phosphate

2) excess magnesium sulfate solution, MgSO4 + H2O is added with ammonia to adjust the ph (appropriate level is 8-9) to form
MgNH4PO4•6H2O

3) solid is isolated by filtration and weighed

Question 15

What is a solute

Answer 15

Thing that gets dissolved

Question 16

What is a solvent

Answer 16

Thing that does the dissolving

Question 17

How to perform calculation after part 2 of experiment

Answer 17

use mass of solid to calculate equivalent mass of “P2O5” (since this is what the manufacturer cites)

• will calculate what percent the mass of P2O5 is of the original mass of the fertilizer
• wi compare to manufactures statement

Question 18

Experimental procedure: how is solution filtered in part 1 and with what compound

Answer 18

Filter hot solution with KOH by pouring through a funnel with filter paper that drips into erlyn flask

Question 19

Experimental provide part 2: how does solution become a solid

List material and process

Answer 19

Use Büchner funnel, filter paper, utility clamp, bench top vacuum, vacuum hose, black rubber adapter

vacuum pulls air through percipitate, can then weigh this

Question 20

What is a percipitate

Answer 20

A solid formed by a change in a solution

Question 21

What was the guaranteed percent of available P205

Answer 21

Available