5. Language Of Chemistry

Question 1

Chemical reaction

Answer 1

a process in which a substance undergoes chemical change to form new substance(s) with new properties is known as a chemical reaction

Question 2

Reactants

Answer 2

substances that take part in the chemical reaction

Question 3

Products

Answer 3

substances formed after reaction is complete

Question 4

What are the 4 characteristics of chemical reactions?

Answer 4

• Molecules of reactants come in close contact with each other
• bond between the atoms of the reactant molecules are broken
• atoms are rearranged by the formation of new bonds to form molecules of the products
• new atoms are neither created nor destroyed

Question 5

Types of chemical reactions (6)

Answer 5

• Combination reaction
• Decomposition reaction
• Single Displacement reaction
• Double Displacement reaction
• Neutralisation reaction
• Combustion reaction

Question 6

Combination reaction

Answer 6

where two or more reactants combine to form a single new product

Question 7

Decomposition reaction

Answer 7

where a single reactant splits into its constituent elements of into other compounds

Question 8

Single displacement reaction

Answer 8

where an element reacts with a compound and replaces the catio of that compound

Question 9

Double displacement reaction

Answer 9

ions of two compounds exchange places in an aqueous solution to form two new compounds

Question 10

Neutralization reaction

Answer 10

reaction between an acid and a base (they have opposite properties and the ability to cancel out/neutralize each other)

Question 11

activation energy

Answer 11

the minimum energy required to start a reaction

Question 12

Ionic compounds

Answer 12

• a compound formed by the oppositely charged ions with attract each other to form a chemical bond

Question 13

9 conditions necessary for chemical reactions to occur

Answer 13

• close contact
• contact in solution (aqueous solutions)
• temperature
• light (photochemical reactions)
• concentration
• surface area
• electricity (electrochemical reactions)
• pressure
• catalyst

Question 14

example of positive and negative catalyst

Answer 14

Positive catalysts (increases rate of reaction) - finely divided iron in Haber’s process
Negative catalyst (decreases rate of reaction) - phosphoric acid in decomposition of Hydrogen Peroxide

Question 15

Aqueous solution

Answer 15

solution of a reactant in water

Question 16

precipitate

Answer 16

an insoluble solid that emerges from a liquid solution in a chemical reaction

Question 17

precipitation reaction

Answer 17

a reaction between two compounds in an aqueous solution state to give two new compounds, one of which in insoluble and precipitates out

Question 18

what are characteristics of occurence of chemical reactions?

Answer 18

• evolution of gas
• change of color
• formation of a precipitate
• change in energy
• change of state

Question 19

by what is evolution of gas indicated

Answer 19

effervescence (vigorous bubble formation)
colored fumes (No2 Gas is brown)
smell (hydrogen sulphide smells like rotten eggs)

Question 20

effervescence

Answer 20

vigorous bubble formation in a liquid due to release of gas

Question 21

how is hydrogen sulphide gas formed

Answer 21

ferrous sulphide (FeS) + Dil. Sulphuric acid

Question 22

3 examples of change in color as a chemical reaction characteristic

Answer 22

1. Grey Iron + RUST = reddish brown ferric oxide (layer formed)
2. Blue Copper Sulphate becomes Green when iron is immersed (due to formation of ferrous sulphate)
3. Green copper carbonate changes to black when heated (copper oxide)

Question 23

2 examples of formation of precipitate

Answer 23

1. As. of ferrous sulphate + As. sodium hydroxide = ferrous oxide (precipitate) - (DIRTY GREEN) + Sodium sulphate
2. Lead acetate + Potassium iodide = Lead iodide (yellow precipitate) + Potassium acetate

Question 24

what is the color of Ferrous oxide and Lead iodide

Answer 24

FeO - dirty ass
Pbl2 - yellow

Question 25

4 types of change in energy

Answer 25

• Evolution of light (Mg + O produces bright white light)
• Evolution/Absorption of heat ( exothermic/endothermic reactions)
• Evolution of Heat and Light (burning of coal)
• Evolution of sound (crackling noise like decripitation)

Question 26

Endothermic & exothermic reaction

Answer 26

Endothermic - reaction where there is absorption of heat
Exothermic - reaction where there is a release of heat

Question 27

1 example of endothermic and exothermic reaction

Answer 27

Endo - Hydrogen + Iodine = Hydrogen Iodide

Exo - Calcium Oxide (quicklime) + Water = Slaked lime (Calcium hydroxide)

Question 28

Decrepitation

Answer 28

crackling noise produced by some chemical reactions (ex. firecrackers)

Question 29

Example of production of electricity as change in energy

Answer 29

Dry cells/batteries used for domestic purposes contain chemicals that react to give electrical energy

Question 30

word equation

Answer 30

when a chemical equation is represented using only the names of the chemicals involved, it is called a word equation

Question 31

3 common acids

Answer 31

• hydrochloric acid (HCL)
• nitric acid (HNO3)
• Sulphuric acid (H2SO4)

Question 32

3 common bases

Answer 32

Sodium Hydroxide (NaOh)

Potassium Hydroxide (KOH)

Ammonium Hydroxide (NH4OH)

Question 33

chemical indicator

Answer 33

any substance that gives a visible sign, usually by color change, of the presence or absence of an acid or a base in a solution

Question 34

examples of chemical indicators

Answer 34

Phenolphthalein

Methyl orange

Question 35

basic property of litmus paper

Answer 35

turns red in acidic medium and turns blue in a basic medium

Question 36

what happens if both red and blue litmus paper remain unchanged when put into a solution

Answer 36

the solution is neutral

Question 37

from where is litmus paper obtained

Answer 37

certain lichens