acids and bases

Question 1

definition of acids

Answer 1

substance that ionises in water to produce H+ ions

Question 2

definition of alkalis

Answer 2

substance that ionises in water to produce OH- ions

Question 3

what are/determine strong acids? [eg. of strong acids; HCL, H2SO4, HNO3]

Answer 3

• it completely ionises (H+) in aqueous solution
• a strong acid undergoes 100% dissociation (eg. every acid molecule will dissociate into ions)

Question 4

what are/determine weak acids? [eg. of weak acids; CH3COOH, H2CO3, organic acids]

Answer 4

• it partially ionised hydrogen ions (H+) in aqueous solution
• a solution of a weak acid contains a large number of undissociated(?) acid molecules and a small number of ions.

Question 5

concentration of acids (concentrated solution vs. diluted solution) diagram

Answer 5

refer to your notes

Question 6

what is acid strength?

Answer 6

it refers to the extent of ionisation of an acid
(eg. hydrochloric acid -strong vs. ethanoic acid- weak)

Question 7

name the 3 different basicity

Answer 7

1. Monobasic acids- acids which on complete dissociation produce one hydrogen ion (or contains one replaceable hydrogen ion) per molecule of the acid
2. Dibasic acids- acids which on complete dissociation produce two hydrogen ion or contain 2 replaceable hydrogen ion) per molecule of the acid
3. Tribasic acids- acids which on complete dissociation produce three hydrogen ion or contains 3 replaceable hydrogen ion) per molecule of the acid

Question 8

properties of acids

Answer 8

• sour taste
• contain mobile ions to conduct electricity
• pH value less than 7
  -turns blue litmus paper to red
• turns universal indicator green to red
• acids react with reactive metals
• acids react with metal carbonates
• acids react with bases (metal oxides and metal hydroxides)

Question 9

properties of bases

Answer 9

• bitter taste
• soapy and feel slippery
• contain mobile ions to conduct electricity
• pH value more than 7
• Turns red litmus paper to blue
• turns universal indicator from green to blue/ purple / violet/ indigo
• bases react with acids
• alkalis react with ammonium salts

Question 10

what are some factors that affect the pH value

Answer 10

strength , basicity, concentration of H+ ions

Question 11

why control the pH of soil?

Answer 11

it is important to control the pH because it will affect the growth and development of plants. And most plants grow best in neutral or slightly acidic soils

hence, to treat acidity in soil, add: liming -to neutralise
-calcium oxide (quicklime)
-calcium hydroxide (slaked lime)

Question 12

importance of pH

Answer 12

1. the body - if pH of 7.4 is changed by one unit, death could result
2. soil - too much fertilisers added to the soil
   - environmental pollution such as acid rain

Question 13

list the types of oxides

Answer 13

1. amphoteric oxides
2. basic oxides
3. neutral oxides

Question 14

list the types of oxides’ properties

Answer 14

1. amphoteric(eg. ZnO, PbO) - react with acids to form a salt and water, behaving like a basic oxide
   - react with bases to form a salt and water, behaving like an acidic oxide
2. basic- metallic oxides
   - solids at room tempt
   - react with acids to form a salt and water only
   - can be soluble(alkalis)/ insoluble(bases) in water
3. neutral(eg. H2O, NO, CO)
   - insoluble in water
   - show neither acidic nor basic properties

Question 15

what are metal oxides

Answer 15

• metal oxide is an Ionic compound that consists of a metal ion and oxide ion
  -all metal oxides are basic oxides except (ZAP- amphoteric oxides)
• properties of metal oxide and metal hydroxides are the same

Question 16

what are non-metal oxides

Answer 16

• non metal oxide is a covalent compound that consists of a non-metal and an oxygen atoms
• all non-metal oxides are usually acidic oxides
• some non-metal oxides (those contain only 1 oxygen) are neutral oxides

Question 17

definition of bases

Answer 17

base is any metal oxide or hydroxide. They contain either the oxide ion (O2-) or hydroxide ion (OH-)