The Acidic Environment (Hsc Chemistry Nsw)

Front 1

Define an acid (Arrhenius definition)

Back 1

A neutral substance that, in solution, produces a positive hydrogen ion and a negative ion.

Front 2

Name three common acids and give their chemical formulae.

Back 2

Hydrochloric acid HCl

Sulfuric acid H2SO4

Nitric acid HNO3

Front 3

Formula for acetic acid

Back 3

CH3COOH

Hint 3

Ethanoic acid

Front 4

Arrhenius definition of a base

Back 4

A substance that gives rise to hydroxide ions in solution

Hint 4

An alternative definition is that bases react with acids to give salts.

Front 5

Name three common bases and give their chemical formulae

Back 5

Sodium hydroxide NaOH

Ammonium hydroxide NH4OH

Calcium hydroxide Ca(OH)2

Front 6

Define and give an example of a neutral substance.

Back 6

Neutral substances do not produce an imbalance in the H+ and OH- ion concentrations in solution.

E.g. CO, NO, H2O, NaCl

Front 7

What is universal indicator?

Back 7

A mixture of several indicators which gives a range of colours over the acid-alkali range.

Front 8

Which indicators are mixed to give Universal Indicator?

Back 8

Phenolphthalein, bromothymol blue, methyl red and thymol blue.

Hint 8

Four different indicators

Front 9

Properties of acids

Back 9

1. They have a sour taste; 2. They can sting or burn the skin; 3. Solutions of acids conduct electricity; 4. They change blue litmus to red; 5. Can react with active metals to produce a salt plus H2. 6. Acid + carbonate -> salt, water + H2 (not for all carbonates but many) 7. Acid + base -> salt + water.

Hint 9

Seven points. Taste; action on skin; electrical conductivity; effect on litmus; three common reactions.

Front 10

Properties of alkalis.

Back 10

1. Soapy or slippery feel; 2. Bitter taste; 3. In solution, good conductors of electricity; 4. Change red litmus to blue; 5. React with acids to give salts + water.

Hint 10

Five points. Feel on skin, taste, electrical conductivity, effect on litmus, one reaction.

Front 11

Litmus colour changes (from acidic to basic)

Back 11

Red - blue

Front 12

Phenolphthalein colour changes (acid first)

Back 12

Colourless - crimson

Front 13

Methyl orange colour changes (acid first)

Back 13

Red - yellow

Front 14

Methyl red colour changes (acid first)

Back 14

Red - yellow

Front 15

Bromothymol blue colour changes (acid first)

Back 15

Yellow - green - blue

Front 16

Universal indicator colour changes (acidic first)

Back 16

Red - orange yellow - green - blue - deep violet

Hint 16

Just like a rainbow, universal indicator gives a range of colours from very acidic to very basic.

Front 17

pH of litmus colour change

Back 17

Around 6.5

Hint 17

Litmus is often used to discriminate between acids and bases because its pKa is close to 7.

Front 18

pH of phenolpthalein colour change

Back 18

Around 9.3

Hint 18

Of the indicators you should learn, phenolpthalein has the highest pKa.

Front 19

pH of methyl orange colour change

Back 19

Around 3.7

Hint 19

Of the indicators you should learn, phenolpthalein has the lowest pKa.

Front 20

pH of methyl red colour change

Back 20

Around 5.0

Front 21

pH of bromothymol blue colour change

Back 21

Around 7.1

Hint 21

The pKa of bromothymol blue is closer to 7 than that of litmus.

Front 22

Define alkali

Back 22

A water soluble compound of the alkali metals (or ammonia) which acts as a strong base, producing a high concentration of hydroxide ions in aqueous solution.

Front 23

Define indicator

Back 23

A substance that indicates when the concentration of a chemical species has passed a certain pH by a change of colour.

Front 24

Acid rain

Back 24

Rain that has a higher concentration of hydrogen ions than pure water.

Front 25

Acidic oxide

Back 25

An oxide that shows acidic properties but not basic properties. That is, it reacts with water to form an acid, and/or reacts with bases to form salts.

Front 26

Examples of acidic oxides

Back 26

NO2, SO2, SO3 and P2O3

Front 27

Basic oxide

Back 27

The oxide of a metal that displays basic properties, but not acidic properties. That is, it reacts with acids to form salts but does not react with alkaline solutions.

Front 28

Examples of basic oxides

Back 28

Na2O, CaO and Fe2O3

Front 29

Dissociation

Back 29

The process where ions that already exist in an ionic compound are released when that compound dissolves in a solvent.

Front 30

Dynamic equilibrium

Back 30

An equilibrium where the rate of forward reaction is the same as the rate of reverse reaction.

Front 31

Endothermic

Back 31

Taking in heat

Front 32

Exothermic

Back 32

Releasing heat

Front 33

Le Chatelier's principle

Back 33

If a system at equilibrium is disturbed, the system will adjust to minimise the effect of the disturbance.

Front 34

Features of a system in equilibrium.

Back 34

1. It is a closed system (no matter or energy enters or leaves the system); 2. Macroscopic properties (colour, temperatures, pressure, state of matter) do not alter; 3. Reactant and product concentrations remain the same; 4. Microscopic changes do occur. 5. The rate of forward reaction equals the rate of reverse reaction. 6. There will always be some reactant and some product.

Front 35

In an equilibrium reaction, increasing the concentration of a reactant...

Back 35

... drives the reaction in the forward direction.

Front 36

In an equilibrium reaction, increasing the concentration of a product...

Back 36

... drives the reaction in the reverse direction.

Front 37

For an equilibrium reaction that is exothermic, raising the temperature...

Back 37

... will shift the reaction so that the concentration of products decreases.

Front 38

For an equilibrium reaction that is endothermic, raising the temperature...

Back 38

... will shift the reaction so that the concentration of products increases.