acids and bases

Question 1

What is the Arrhenius definition of acids?

Answer 1

An acid is a substance that releases H+ ions when dissolved in water.

Question 2

Name 3 examples of strong acids and their chemical formulas.

Answer 2

Hydrochloric acid: HCl
Sulfuric acid: H2SO4
Nitric acid: HNO3

Question 3

Name at least one example of a weak acid and its chemical formulas.

Answer 3

Ethanoic acid: CH3COOH
Carbonic acid: H2CO3
Phosphoric acid: H3PO4

Question 4

What are the properties and characteristics of acids?

Answer 4

• Acids taste sour
• Acids turn blue litmus paper red
• Strong acids are electrolytes that dissolve in water to form solutions that can conduct electricity due to the presence of mobile ions that act as charge carriers

Question 5

What is the Arrhenius definition for bases?

Answer 5

A base is a substance that releases OH- ions when dissolved in water. 
take note: ALKALIS are a special class of bases that have the ability to dissolve in water

Question 6

What is “the other” definition of bases (that arose because most bases were insoluble)?

Answer 6

A base is a substance that reacts with an acid to give SALT and WATER only. All metal oxides and hydroxides can act as bases.

Question 7

Name 3 examples of soluble bases and their chemical formulas.

Answer 7

Sodium hydroxide: NaOH
Potassium hydroxide: KOH
Ammonia: NH3 (it can react with water to release OH- ions)

Question 8

Name some insoluble bases and their chemical formulas.

Answer 8

Iron (III) oxide: Fe2O2
Magnesium oxide: MgO
Copper (II) oxide: CuO
Aluminium hydroxide: Al(OH)3
Iron (II) hydroxide: Fe(OH)2
(calcium hydroxide: Ca(OH)2)

Question 9

What are the properties and characteristics of alkalis?

Answer 9

• Alkalis taste bitter and have a soapy feel
• Alkalis turn red litmus paper blue
• Strong alkalis are strong electrolytes. They can dissolve in water to form solutions that can conduct electricity due to the presence of mobile ions that act as charge carriers

Question 10

Acids react with reactive metals to form a __ and ___ __
Acids react with metal carbonates/metal hydrogen carbonates to form a __, ___ and ___ ___ __
Acids react with bases (metal oxides/hydroxides) to form a __ and ___

Answer 10

Acids react with reactive metals to form a salt and hydrogen gas
Acids react with metal carbonates/metal hydrogen carbonates to form a salt, water and carbon dioxide gas
Acids react with bases (metal oxides/hydroxides) to form a salt and water

Question 11

What are some unreactive metals?

Answer 11

Copper, silver, gold
(also lead doesn’t appear to react with dilute hydrochloric acid and dilute sulfuric acid because lead (II) chloride/sulfate is produced which is insoluble in water and produces a coating around the metal which prevents the metal from further reaction with the acid)

Question 12

What is the test for hydrogen gas?

Answer 12

Place a lighted splint at the mouth of the test tube when effervescence is observed. Hydrogen gas present will extinguish the lighted splint with a “pop” sound.

Question 13

What is the test for carbon dioxide?

Answer 13

Bubble the gas through limewater (aqueous calcium hydroxide). Carbon dioxide forms a white precipitate with limewater.

Question 14

What is the test for ammonia gas?

Answer 14

Ammonia gas is colourless and pungent. It turns moist red litmus paper blue.

Question 15

Dissociation is…

Answer 15

Dissociation is the splitting of a soluble substance in water into ions, which are now free to move about in a solution.

Question 16

How is the strength of an acid or base determined?

Answer 16

The strength of an acid or base refers to the extent to which an acid or base dissociates when dissolved in water.

Question 17

An electrolyte is…

Answer 17

An electrolyte is a substance that conducts an electric current as a result of its dissociation into ions when dissolved in a solvent such as water.

Question 18

A strong electrolyte ____ dissociates in a solution and contains only ___.

Answer 18

A strong electrolyte completely dissociates in a solution and contains only ions.

Question 19

A strong acid is defined as an acid that dissociates (or ionises) _____ in water to form ____ ions , __.

Answer 19

A strong acid is defined as an acid that dissociates (or ionises) completely in water to form hydrogen ions , H+.

Question 20

A weak acid is an acid that dissociates (or ionises) ____ in water to form ____ ions, __.

Answer 20

A weak acid is an acid that dissociates (or ionises) partially in water to form hydrogen ions, H+.

Question 21

Weak acids are also weak ______, which conduct only a ___ electrical current as it contains a relatively ___ concentration of ___ __.

Answer 21

Weak acids are also weak electrolytes, which conduct only a small electrical current as it contains a relatively lower concentration of mobile ions.

Question 22

Concentration is…

Answer 22

Concentration is the amount of substance (solute) dissolved in a fixed volume of solution.

Question 23

What is one thing that distinguishes strength and concentration?

Answer 23

The strength (extent of dissociation in water) of an acid or base cannot be changed, while the concentration of an acid or base can be changed.

Question 24

Acids are classified as ____, ____ or ____ depending on the number of _ atoms in a molecule that are able to form __ ions when it ____ in water.

Answer 24

Acids are classified as monobasic, dibasic or tribasic depending on the number of H atoms in a molecule that are able to form H+ ions when it dissociates in water.

Question 25

Are the basicity and strength of an acid related?

Answer 25

No. An acid can be tribasic but also be a weak acid.

Question 26

To compare the strength of two unknown acids, they have to have the same…

Answer 26

• Basicity

- Concentration

Question 27

How do you measure the strength of an acid?

Answer 27

• pH
• brightness of bulb (strong acids are electrolytes)
• rate of reaction
  (this was like notes on the side so probably sth mr lim just briefly mentioned during lessons but it’s good to know I guess)

Question 28

The smaller/lower the pH, the higher the __ concentration and the more ___ the solution. The larger/higher the pH, the lower the __concentration and the more ___ the solution.

Answer 28

The smaller/lower the pH, the higher the H+ concentration and the more acidic the solution. The larger/higher the pH, the lower the H+ concentration and the more alkaline the solution.

Question 29

Name 2 types of metal oxides and what they react with + their products.

Answer 29

Basic oxides:
- Reacts with only acids to form salt and water
- Some insoluble, some soluble (in water)
examples: potassium oxide, sodium oxide, lithium oxide, calcium oxide, barium oxide, (soluble)
magnesium oxide, copper (II) oxide, iron (II) oxide, iron (III) oxide (insoluble)
Amphoteric oxides:
- Reacts with acids and bases to form salt and water
- All insoluble (in water)
examples: zinc oxide, aluminium oxide, lead (II) oxide

Question 30

Name 2 types of non-metal oxides and what they react with + their products.

Answer 30

Acidic oxides:
- Reacts with only bases to form salt and water
- Some insoluble, some soluble (in water)
examples: nitrogen dioxide, carbon dioxide, phosphorous (V) oxide, sulfur dioxide, sulfur trioxide (soluble)
silicon dioxide (insoluble)
Neutral oxides:
- Does not react with an acid or a base
- All insoluble (in water)
examples: carbon monoxide, nitric oxide (also known as nitrogen (II) oxide)

Question 31

What are some uses of acids and bases?

Answer 31

Acids:
- fertilisers, detergents, battery acid in cars, cleaning agent, food preservative/flavour enhancer, food and beverages, explosives, in the manufacture of chemicals, fizzy drinks (effervescence and carbonation !!)
Bases:
- antacid, refractory bricks, toothpaste, soap, reduce acidity in soil (slaked lime aka calcium hydroxide), absorb acidic gas, fertilisers