Chemistry T5B: Acids, bases, salts and oxides

Define an acid

A substance that dissolves and dissociates in water to form hydrogen ions and the corresponding anions

Describe the role of water in acids

- Acids only show their properties when dissolved in water

- Hydrogen ions give an acid its characteristic properties

Define the basicity of an acid

Number or hydrogen ions produced per acid molecule

Define and describe the strength of acids

- Extent of dissociation when dissolved in water

- Strong acids fully dissociate to form a high concentration of hydrogen ions

- Weak acids partially dissociate to form a low concentration of hydrogen ions

Define the concentration of an acid

Number of acid molecules per unit volume

State the physical properties of acids

- Sour taste

- Turns blue litmus red

- Turns universal indicator red/orange/yellow

- pH < 7

- Good conductors of electricity when dissolved in water

Acid + Reactive metal =

Salt + Hydrogen gas

Acid + Base =

Neutralization reaction

Salt + Water

Acid + Carbonate/Hydrogen carbonate =

Salt + Water + Carbon dioxide gas

State the uses of sulfuric acid

- Manufacture of fertilizers

- Manufacture of detergents

- Used in car battery acids

State the uses of hydrochloric acid

- Rust removal

State the uses of phosphoric acid

- Used in foods and beverages to achieve a sour taste

Define a base

A substance that reacts with acids to form a salt and water only. Bases are usually metal oxides or hydroxides

Define an alkali

A base that can dissolve and dissociate in water to form hydroxide ions and the corresponding metal ions

Define and describe the strength of an alkali

- The extent an alkali dissolves and dissociates in water to form hydroxide ions

- Strong alkalis dissolve and dissociate completely in water to form a high concentration of hydroxide ions

- Weak alkalis dissolve dissolve and dissociate partially in water to form a low concentration of hydroxide ions

State the physical properties of alkalis

- Bitter, soapy

- Turns red litmus blue

- Turns universal indicator blue/indigo/violet

- pH>7

- Good conductor of electricity when dissolved in water

Alkali + Acid =

Neutralization reaction

Salt + Water

Alkali + Ammonium salt =

Salt + Water + Ammonia gas

Alkali + Metal salt solution =

Insoluble metal hydroxide + Another salt

State the compound taken for gastric pain relief

Magnesium oxide

State the uses of magnesium oxide

- Antacid for gastric pain relief

- Manufacturing of refractory bricks

State the compounds used in the manufacturing of soap

Sodium hydroxide and potassium hydroxide

State the compounds used to reduce acidity in soil

Calcium hydroxide and calcium oxide

Describe the water of crystallization

- Many salts will combine with water molecules to form crystals

- These salts are perfectly dry but held together by water molecules

Describe anhydrous salts

Salts without water of crystallization

Describe the process of removing water of crystalization

- Heat the sold

- Colorless liquid forms at too and sides of test tube

- Change in color(If any)

Describe the 2 tests for water

- Using anhydrous cobalt(II) chloride paper

- Blue > pink

- Using anhydrous copper(Ii) sulfate

- White > blue

Define an acidic oxide and its properties

- Oxides of non-metals

- Dissolves in water to form acids

- Reacts with alkalis to form salt and water

Define a basic oxide and its properties

- Oxides of metals

- Dissolves in water to form an alkali

- Reacts with acids to form salt and water

Define an amphoteric oxide and its properties

- Oxides of metals

- Insoluble in water

- Reacts with both acids and alkalis to form salt and water

Give 3 examples of amphoteric oxides

- Zinc Oxide

- Aluminum Oxide

- Lead (II) Oxide

Define a neutral oxide and its properties

- Oxides of non-metals

- Insoluble in water

- Does not react with acids or alkalis

- Usually monoxides

Give 3 examples of neutral oxides

- Carbon monoxide

- Nitrogen monoxide

- Hydrogen monoxide (water)

Describe the term pH

A measure of the concentration of hydrogen ions

Define the term indicator

Solutions that change colors in solutions with different pH values

State the methods of measuring pH

- Universal indicator paper or solution

- pH meter

- Data logger with pH sensor

State the color of Methyl Orange in alkaline or acidic solutions

Red in acidic

Yellow in alkaline

State the color of Phenolpthalein in alkaline or acidic solutions

Colorless in acidic

Pink in alkaline

State the color of Litmus in alkaline or acidic solutions

Red in acidic

Blue in alkaline

State the pH where plants grow best

pH 5-7

Give reasons on why soil may become unsuitable for plant growth

- Over fertilization

- Acid rain

State and describe the method of controlling pH in Soil

Liming

- Acidic soil is treated with quicklime or slaked lime

- Bases react with acids to increase pH if soil

State the chemical name and symbol for quicklime

Calcium oxide

CaO

State the chemical name and symbol for slaked lime

Calcium hydroxide

Ca(OH)2