Chemical Reactions And Equations

Question 1

When can we say that a chemical reaction takes place?

Answer 1

When a chemical change occurs.

Question 2

Lead Nitrate + Potassium Iodide

Answer 2

Lead Iodide and Potassium Iodide

Question 3

Zinc granules + Sulphuric Acid

Answer 3

Zinc Sulphate and Hydrogen

Question 4

What can help us determine if a chemical reaction has taken place?

Answer 4

+ Change in state
+ Change in colour
+ Evolution of a gas
+ Change in temperature

Question 5

What are reactants?

Answer 5

The substances that undergo chemical change in the reaction.

Question 6

What are products?

Answer 6

The new substances formed during the reaction.

Question 7

What does the arrowhead indicate?

Answer 7

The direction of the equation.

Question 8

What is a chemical equation?

Answer 8

A chemical equation is a representation of a chemical equation.

Question 9

What is a skeletal equation?

Answer 9

A equation which is unbalanced and the mass is not the same on both sides of the equation.

Question 10

What is hit-and-trial method of balancing chemical equations?

Answer 10

Making trials to balance the equation by using the smallest whole number co-efficient.

Question 11

Solid

Answer 11

(s)

Question 12

Liquid

Answer 12

(l)

Question 13

Gaseous

Answer 13

(g)

Question 14

Aqueous

Answer 14

Present as a solution in water; (aq)

Question 15

Where are the reaction conditions indicated?

Answer 15

Temperature, pressure, catalyst, etc. are indication above and/or below the arrow.

Question 16

What do chemical reactions involve?

Answer 16

Making and breaking of bonds between atoms to produce new substances.

Question 17

Define combination reaction.

Answer 17

A reaction in which a single product is formed from two or more reactants.

OR

When two or more substances combine to form a single product.

Question 18

What are exothermic reactions?

Answer 18

Reactions in which heat is released along with the formation of products.

Eg.: Burning of natural gas, respiration, decompostition of vegetable matter.

Question 19

Define Decomposition reaction.

Answer 19

When a single reactant breaks down to give simpler products.

Eg.: Calcium Carbonate to Calcium Oxide and CO2.

Question 20

What is thermal decomposition?

Answer 20

When decomposition is carried out by heating.

Eg.: Lead Nitrate heating > Nitrogen Dioxide and Lead Oxide

Question 21

What is photolytic decomposition?

Answer 21

When chemical substances are broken down by photons.

Eg.: AgCl and AgBr > Both used in black and white photography

Question 22

What are endothermic reactions?

Answer 22

Reactions in which energy is absorbed.

Eg.: Ammonium Chloride + Barium Hydroxide.

Question 23

What is electrolytic decomposition?

Answer 23

Decomposition that occurs when electricity is passed through it.
Eg.: Water splits into H2 and O2 when electricity is passed through it.

Question 24

What is displacement reaction?

Answer 24

When a more reactive metal displaces a less reactive metal from its compound.
Eg.: Iron + Copper Sulphate –> Iron Sulphate + Copper
Lead + Copper Chloride –> Lead Choride + Copper

Question 25

What is double displacement reaction?

Answer 25

A reaction in which there is an exchange of ions between the reactants.
Eg.: Sodium Sulphate + Barium Chloride –> Sodium Chloride + Barium Sulphate