Conservation of Mass
The law of conservation
of mass states that
mass is neither created
nor destroyed during a
chemical reaction—it is
conserved.
Conservation of Mass
Conservation of Mass
Conservation of Mass
From a laboratory process designed to separate water into hydrogen and
oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of
oxygen. How much water was originally involved in the process?
Conservation of Mass
A student carefully placed 15.6 g of sodium in a reactor supplied with
an excess quantity of chlorine gas. When the reaction was complete, the
student obtained 39.7 g of sodium chloride. Calculate how many grams
of chlorine gas reacted. How many grams of sodium reacted?
A 10.0-g sample of magnesium reacts with oxygen to form 16.6 g of
magnesium oxide. How many grams of oxygen reacted?
Conservation of Mass
Challenge
106.5 g of HCl(g) react with an unknown amount of N H 3(g)
to produce 157.5 g of N H 4Cl(s). How many grams of N H 3(g)
reacted? Is the law of conservation of mass observed in the reaction?
Justify your answer.
Demonstration of a synthesis of ammonium
chloride. Concentrated ammonia and hydrochloric
acid solutions are added to two gas-washing
bottles, respectively. Using rubber pumps, air
(acting as gas-carrier) is injected in the gaswashing tubes causing the streams of ammonia
and hydrogen chloride in air to collide and react
giving the solid product, ammonium chloride.
Conservation of Mass
French scientist Antoine Lavoisier (1743–1794)
was one of the first to use an analytical balance to
monitor chemical reactions. He studied the
thermal decomposition of mercury(II) oxide,
known then as calx of mercury.
Mercury(II) oxide is a powdery red solid. When it
is heated, the red solid reacts to form silvery liquid
mercury and colorless oxygen gas. The color
change and production of a gas are indicators of a
chemical reaction.
When the reaction occurs in a closed container,
the oxygen gas cannot escape and the mass
before and after the reaction can be measured.
The masses will be the same.
The law of conservation of mass is one of the
most fundamental concepts of chemistry