Lesson: Chemical Reactions and Equations
should a magnesium ribbon be cleaned before burning in air?
Magnesium is a
highly reactive metal. It reacts with oxygen to form a layer of magnesium oxide
on its surface. This layer is quite stable and prevents further reaction of
magnesium with oxygen. Hence, the magnesium ribbon is cleaned to remove this
the balanced equation for the following chemical reactions.
a balanced chemical equation with state symbols for the following reactions.
Solutions of barium chloride and sodium sulphate in water react to give
insoluble barium sulphate and the solution of sodium chloride.
Sodium hydroxide solution (in water) reacts with hydrochloric acid
solution (in water) to produce sodium chloride solution and water.
solution of a substance ‘X’ is used for white washing.
Name the substance ‘X’ and write its formula.
Write the reaction of the substance ‘X’ named in (i) above with water.
(i) The substance ‘X’ is calcium oxide.
Its chemical formula is CaO.
is the amount of gas collected in one of the test tubes in Activity1.7
(electrolysis of water) double of the amount collected in the other? Name this gas.
activity is electrolysis of water. In this activity, hydrogen and oxygen are
collected in separate test tubes. A molecule of water ( ) contains
two hydrogen atoms and one oxygen atom. Therefore, the hydrogen and oxygen
produced during electrolysis of water is in the ratio 2:1. Thus, the amount of
hydrogen gas collected in one of the test tubes is double the amount of oxygen
gas collected in the other.
does the colour of copper sulphate solution change when an iron nail is dipped
is more reactive than copper. When an iron nail is dipped in a copper sulphate
solution, which is blue in colour, iron displaces copper from the solution
and forms ferrous sulphate, which is green in colour.
the colour of the copper sulphate solution changes from blue to green.
an example of a double displacement reaction.
carbonate reacts with calcium chloride to form calcium carbonate and
sodium chloride. This is a double displacement reaction.
the substances that are oxidised and the substances that are reduced in the
(i) Sodium (Na)
is oxidised as it gains oxygen and oxygen gets reduced.
(ii) Copper oxide (CuO) is
reduced to copper (Cu) while hydrogen ( ) gets
oxidised to water ( ).