Chemistry Reference
In-Depth Information
E5.18: Reaction of Tube Cleaner (NaOH-Al-type)
Problem: The bathroom chemical “tube cleaner” can be introduced and analyzed for
the repetition of discussed facts on substances like alkaline metal hydroxides and
bases. The label on a container of tube cleaner reveals the ingredients sodium
hydroxide and aluminum. In addition to a white substance in granular form, little
silver-colored metal splinters can be found in the tube cleaner. When water is added a
strong exothermic and alkaline reaction sets in. Adding paper demonstrates the
decomposition by the reaction of hot, concentrated sodium hydroxide solution. Pro-
duced ammonia gas may be discussed (see also the explanation of E8.1 in Chap. 8).
Material: Test tubes, tube cleaner (NaOH-Al-type) (C), universal indicator paper,
hydrochloric acid (C), wooden splint, pieces of newspaper.
Procedure: The mixture of substances is to be analyzed by visual inspection. The
white powder is to be separated from the metal splinters. The powder is to be
dissolved in water; the solution is to be tested with indicator paper. The metal is to
be put into hydrochloric acid and the emerging gas is to be collected and tested for
hydrogen with a burning wooden splint. A small amount of water is to be added to
the mixture, little pieces of newspaper are to be added and observed.
Observation: The solution colors the indicator paper deep blue. The metal dissolves
with formation of a colorless gas, this gas combusts in air with a whistling noise:
hydrogen. The mixture reacts with water to a very hot solution under gas formation;
the concentrated solution decomposes pieces of paper.
E5.19: Reaction of Alkaline-Earth Metals with Water
Problem: To estimate the learning success it can be tested whether students can
transfer the familiar reactions of alkaline metals with water to similar reactions of
magnesium and calcium with water. The formation of hydroxides and hydrogen is
well known, but solid hydroxides accumulate as suspensions. The composition
M(OH)
2
,(M
Ca, Mg) has to be given as the formula for calcium hydroxide or
magnesium hydroxide, and then reaction equations can be derived.
Material: Glass bowl, glass cylinder with cover glass, outflow pipe, infusible test
tube, magnesia groove, test tubes, perforated stopper, glass tube, universal indicator
paper; magnesium turnings (F), calcium turnings (F), sand.
¼
Magnesium shavings
Wet sand
