Illustrated Guide to Home Chemistry Experiments

Chapter 9 Laboratory: Introduction to Chemical Reactions and Stoichiometry 173

CUTIOA nS

Concentrated hydrochloric acid is corrosive and emits

hazardous fumes. Keep the test tube pointed away

from you and in a safe direction in case the reaction

proceeds too vigorously. Spilled acid can be neutralized

with an excess of solid sodium bicarbonate (baking

soda). Hydrogen gas is extremely flammable. Although

only a small amount of hydrogen is generated in this

experiment, it may “pop” when ignited, startling you and

causing you to drop the test tube. Do not sniff the test

tube during or after the reaction, because the heat of

the reaction liberates irritating hydrogen chloride gas.

Perform this experiment outdoors, or under an efficient

fume hood or exhaust fan. Wear splash goggles, gloves,

and protective clothing.

z

POCEDURER

dAUL. Rp joNES CommENTS:

One can also do this on a slightly larger scale and catch

the hydrogen in a balloon, which can later be ignited, to

amusing effect, in a suite-mate’s shower. Or so I’m told.

This laboratory has two parts. In Part I, we’ll observe a single-
displacement reaction in which aluminum metal displaces
hydrogen from hydrochloric acid. In Part II, we’ll observe another
single-displacement reaction in which iron metal displaces
copper ions from a solution of copper sulfate.

PRTI:A
1.f you have not already done so, put on your splash I
goggles, gloves, and protective clothing.

2. Transfer about 5 mL of concentrated hydrochloric acid
   to one of the test tubes in your test tube rack.


3. Ignite a toothpick or wood splint, and hold it just above
   the mouth of the test tube to verify that no flammable
   gas is present.


4. Weigh about 1 g of aluminum granules, and transfer
   them to the test tube with the hydrochloric acid.
   (Depending on the fineness of the aluminum metal, the
   reaction can be quite vigorous, so make sure that the
   mouth of the test tube is pointing in a safe direction
   in case liquid is ejected.) It takes a moment for the
   hydrochloric acid to remove the aluminum oxide that
   coats the aluminum metal. After this oxide coating is
   removed, the reaction proceeds vigorously (Figure 9-3).


5. Ignite another toothpick or wood splint and hold the
   burning end just above the top of the test tube. The
   hydrogen gas produced by the reaction ignites. (Don’t
   be startled if the gas ignites with a noticeable pop; the
   small amount of hydrogen gas produced by this reaction
   is harmless.)

FIGURE 9-3: Aluminum metal reacting with hydrochloric acid

PRTII:A

1.ou have not already done so, put on your splash If y

goggles, gloves, and protective clothing.

2. Weigh about 2.5 g of copper sulfate pentahydrate and add
   it to a test tube in the rack.


3. Transfer about 10 mL of water to the test tube, and swirl
   or shake the test tube until the copper sulfate dissolves
   completely.


4. Use the sandpaper or emery board to clean the surface
   of the nail thoroughly. Remove all oxidation and leave a
   shiny, bright surface.


5. Tie the thread around the head of the nail, and carefully
   submerge the nail in the solution of copper sulfate,
   keeping the thread outside the tube.


6. After 15 minutes and then again every 15 minutes,
   withdraw the nail, and observe and note any visible
   changes, and then return it to the copper sulfate
   solution. Continue this until no further change is evident
   (Figure 9-4).