Question

(a) What are the various ways in which a chemical equation can be made more informative? Give examples to illustrate your answer.
(b) Write balanced chemical equation from the following information
An aqueous calcium hydroxide solution (lime water) reacts with carbon dioxide gas to produce a solid calcium carbonate precipitate and water.

Answer 1

Ca(OH)2 (aq)+ CO2 (g)---3000°C-----> CaCO3^ +H2O(l)

A chemical equation can be made more informative by :

1. Writing the chemical states of the reactants and products such as s for solids , l for liquids, g for gases and aq. for aqueous solution.

2. Writing the temperature or atmospheric pressure on the arrow.

3. An arrow pointing upwards shows the formation of precipitate.

4. An arrow pointing downwards shows the evolution of gas.

5. Writing the colours of the reactants and products to show colour change.

6. Writing '+Heat' on the reactant side to state that the reaction is exothermic.

7.Writing '-Heat' on the product side to state that the reaction is endothermic.

Answer 2

Explanation:

(a) Chemical equation:

• A chemical reaction is made more informative with the symbols used in the equation. A chemical equation is used to define the reaction taking place under certain circumstances with certain material to produce particular product in particular state.

Some of the symbols are given below:

• The state of the reactants and products are defined with the (s) if it is solid; (cr) if it is crystal; (l) if it is liquid; (g) if it is gas; (aq) if it is aqueous solution.
• The down arrow defines the product is a precipitate.
• The up arrow defines the product formed gas.
• The arrow pointed to right defines that the product is formed.
• The two arrows pointed in opposite directions indicates the reaction is a reversible reaction.
• The right arrow with a triangle on the upper side indicates the reactants are heated.
• The right arrow with a unit of pressure on the upper side indicates pressure of the reaction.
• The right arrow with a unit of temperature on the upper side indicates temperature of the reaction.
• The right arrow with a chemical formula of element/compound defines the reactants are catalysed by the particular element/compound.
• A chemical reaction with $e^-$ defines electrolysis process.

(b) Balanced chemical reaction:

$2 C a(O H)_{2(a q)}+2 C O_{2(g)} \rightarrow 2 C a C O_{3(g)} \downarrow+2 H_{2} O_{(l)}$

With the information given in the question above equation is formed.