8th Grade Science – Professor Shai
Synthesis of Zinc Chloride
Section 6.4 – Page 118
The theme of this experiment is to exhibit the law of constant proportions. Namely, that compounds are composed of substances using the same proportions of mass. In this case, a fixed amount of hydrochloric acid will be mixed with zinc to produce zinc chloride.
zinc chloride from zinc and hydrochloric acid, and measure
the ratio of
the reacting zinc to the zinc chloride produced. Each
have 10 cc of acid and varying mass of zinc. With a
of zinc, the zinc will all be used up and there will be acid
after the reaction. With a large amount of zinc, all
will be used up, and there will be zinc leftover after the
reaction. The goal is to find out how much zinc
reacts, and how
much zinc chloride is produced.
10 cc of hydrochloric acid from me and keep it in a
some zinc from me - you will receive anywhere from .5 to 4
grams. Mass it to make sure you know how much you
Mass of zinc to start =
the zinc in test tube, and have the test tube sit inside a
of cold water. Pour the acid into the test
reaction should give off a lot of heat - hence the beaker
water. It also produces hydrogen. The reaction
ends up with
a liquid in which zinc chloride is dissolved, and perhaps
zinc that will be visible. Let it sit overnight.
-- we will discuss the ideas behind this experiment the
of the day.
Mass an evaporation dish and pour the liquid from the
it. If any zinc remains, do not pour it into the
Leave the excess zinc in the test tube.
Mass of evaporation dish =
the test tube (and zinc if any) with 5 cc water and pour
water into the evaporation dish. This is done in
order to get
acid, zinc chloride, etc) except the zinc into the dish.
and mass the leftover zinc, if any. Calculate the
zinc that reacted.
test tube and zinc =
of test tube
Mass of remaining zinc = Mass of test tube and zinc - Mass of test tube =
Mass of reacting zinc = Mass of zinc to start - Mass of remaining zinc =
gently heat the evaporation dish until the liquid (acid,
and water) is gone and there is only precipitate (zinc
left. Danger: You must wear goggles! If
splatters on your face or eyes you will be injured.
not to let any substance splatter out when you
are heating. If you heat too long, the liquid will
and the solid precipitate of zinc
chloride will start to melt. You can do this on
purpose to make
liquids are gone, but then let the melted zinc chloride
cool back to
solid to be sure. You must make sure the zinc
chloride is dry
because otherwise, when you mass it you will be massing it
the zinc chloride and the dish as soon as it cools to the
touch. Leaving it too long, will allow it to absorb
the air and mess up your mass.
zinc chloride and dish =
Mass of zinc chloride produced = Mass of evaporation dish - Mass of zinc chloride and dish =
the ratio of the mass of zinc that reacted to the mass of
zinc chloride produced.
Mass of reacting zinc / Mass of zinc chloride