Language of Chemistry and Chemical Reactions

Question 1

Definition of chemical reaction

Answer 1

A chemical change is a permanent change in which the chemical composition of a substance is changed and one or more new substances with different chemical compositions and different properties are formed

Question 2

Name the characteristics of a chemical change

Answer 2

1. Permanent and irreversible
2. Composition changes
3. Exothermic or endothermic
4. Total mass remains the same

Question 3

Define chemical bond

Answer 3

Is the force that holds the atoms of a molecule together as a compound

Question 4

Explain and give an example, as to why mixing or close contact is a necessary for chemical change

Answer 4

1. Chemical chemical reaction occurs when two substances are mixed with solid states.
2. iodine and phosphorus, lead nitrate and potassium iodide make lead iodide

Question 5

Explain, and give an example, why solution is necessary for a chemical change

Answer 5

1. in some cases, a chemical reaction occurs in substances are mixed in either mole or aqua states
2. sodium nitrate and silver chloride.
3. Oxalic acid crystals and sodium carbonate.

Question 6

Explain why heat is necessary for chemical change.

Answer 6

1. Copper carbonate decomposes into copper oxide and copper carbon dioxide on heating.
2. Lead nitrate decomposes on heating, leaving lead monoxide(yellow)nitrogen dioxide(brown)and oxygen.

Question 7

Explain why light necessary for chemical change.

Answer 7

Some chemical chemical reactions take place by the action of light. They are called photochemical reactions or photolysis
1. Photosynthesis.
2. Hydrogen and chlorine.
3. Silver nitrate and hydrogen peroxide.(kept brown bottles because decomposed in presence of light)

Question 8

Explain why electricity is necessary in chemical change.

Answer 8

1. Electrochemical reactions.
2. Electrolysis of acidulated water gives hydrogen and oxygen.
3. Passing through molten sodium chloride, sodium and chlorine are separated.

Question 9

Why is pressure necessary for chemical change?

Answer 9

1. Mercury chloride and potassium iodide when crushed together, give mercury iodide.
2. Nitrogen and hydrogen when subjected to pressure produce ammonia.

Question 10

Name some chemical reactions produced by absorption of sound energy.

Answer 10

Acetylene breaks up into carbon and hydrogen by absorbing sound energy

Question 11

Name by a catalyst is necessary for chemical reactions

Answer 11

Potassium chloride decomposes faster in the presence of manganese dioxide
2. Ammonia reacts with oxygen to produce nitric oxide and H2O in the presence of platinum.

Question 12

What is the catalyst?

Answer 12

Some chemical reactions need a catalyst to accelerate or diesel rate, the rate at which they occur

Question 12

What is the positive catalyst name, an example?

Answer 12

Catalyst accelerate is the rate of reaction, example, manganese dioxide.
1. Enzymes act as catalyst in biochemical reactions.

Question 13

What is a promoter?

Answer 13

Substances that influence the rate of a chemical reaction by improving the efficiency of the catalyst

Question 14

What is the negative catalyst name, an example?

Answer 14

A catalyst that retards the rate of chemical reaction
1. A the rate of oxidation of chloroform decreases with alcohol.
2. Phosphoric acid react the rate of decomposition of hydrogen peroxide.

Question 14

Name an example of a promoter

Answer 14

In the manufacture of ammonia iron, a cat and mole denim as promoter

Question 14

Name the characteristics of chemical r reactions

Answer 14

Evolution of gas, change of colour formation of precipitate and change of state

Question 14

What is effervescence

Answer 14

The formation of gas bubbles in a liquid during reaction is called FO essence.

Question 15

What is slake lime used for?

Answer 15

Lime is used for white washing when a solution of snake is applied to the walls. Calcium hydroxide reacts slowly with carbon dioxide present in the atmosphere to form a thin layer of calcium carbonate.
Calcium hydroxide twice is known as lake line

Question 16

What is combination or synthesis reaction?

Answer 16

Reaction in which two or more substances combine together to form a single substance is called as combination or react synthesis reaction

Question 17

What is decomposition reaction?

Answer 17

The chemical reaction in which a compound splits into two or more simple substances is called decomposition reactions. These products do not combine to form the original compound.

Question 18

How can decomposition occur?

Answer 18

Decomposition can occur with the presence of heat or light or by the passage of an electric current

Question 19

What happens if silver chloride is exposed to sunlight?

Answer 19

If silver chloride is exposed to sunlight undergoes photochemical decomposition, forming a grey metal, silver, and greenish, yellow gas

Question 20

What is thermal decomposition?

Answer 20

Decomposition reaction that is brought about by heat without any combination on cooling is known as thermal decomposition

Question 21

Explain decomposition reactions in our body

Answer 21

Digestion of a food is an example
Starch present in the food. We eat decomposes into glucose and sugar proteins, undergo decomposition to form amino acids, fats and oil, decomposed to form fatty acids and oxidised by respiration into carbon dioxide and water.

Question 22

What is thermal dissociation?

Answer 22

A reversible decomposition reaction about only by heat is thermal association

Question 23

What is displacement reaction?

Answer 23

It is a chemical change in which a more active element is select active element from its salt solution

Question 24

What is double decomposition reaction?

Answer 24

This is the type of chemical change in which two compounds in a solution react to form two new compounds by noottinaalu mutual exchange of radicals

Question 25

What is precipitation reaction?

Answer 25

A chemical reaction reaction in which two compounds in aqua state, react to form insoluble salt

Question 26

Precipitation is the formation of a solid either:

Answer 26

1. When two solutions are mixed.
2. A gas is bubbled into the solution.

Question 27

What is neutralisation reaction?

Answer 27

Neutralisation reaction is the reaction between an acid and base that form salt and water

Question 28

What is chemical energy?

Answer 28

Every substance has a fixed amount of stored energy, which is in the form of potential energy and is referred to chemical energy

Question 29

What are fuels?

Answer 29

Substances such as methane, which undergo combustion readily and give large amount of energy

Question 30

What is an exothermic reaction?

Answer 30

A chemical reaction in which heat is given out is called hexa Tomic reaction

Question 31

Example of exothermic reaction

Answer 31

Carbon plus oxygen gives carbon dioxide and heat
2. Nitrogen plus hydrogen gives ammonia and heat
3. Quick lime plus water gives slaked lime plus heat.

Question 32

What is an endothermic reaction?

Answer 32

A chemical reaction in which heat is absorbed is called endothermic reaction

Question 33

Examples of endothermic reaction

Answer 33

Carbon plus sulphur gives carbon di sulphide

2. Nitrogen plus oxygen gives nitrogen oxide.
3. Calcium carbonate decomposes to calcium oxide and calcium carbon dioxide.

Question 34

What is the photo chemical reaction given example?

Answer 34

It’s a reaction that occurs with the absorption of light energy
1. Photosynthesis.
2. Silver nitrate decomposes to give silver plus nitrogen dioxide plus oxygen.

Question 35

What is an electro chemical reaction?

Answer 35

It is the reaction occurs with absorption of electrical energy
1. Potassium chloride on electric current gives potassium plus chlorine.
2. Acidulated water breaks down into hydrogen and oxygen.