Chemistry: Acids. Bases and Salts

acids

acids

• proton donors

• react with a base to form salt and water

• react with water to form hydronium ions

properties of acids

• colourless

• sour

• pH of less than 7 (turn blue litmus paper red)

• corrosive

• electrolytes

acid + metal

salt + hydrogen

acid + base

salt + water

acid + (metal)hydrogen carbonate

salt + carbon dioxide + water

basicity of an acid

the amount of hydrogen ions given off by a single molecule when dissolved in water

types of basicity

monobasic, dibasic, tribasic

acid anhydride

a covalent compound that reacts with a base to produce salt and water or dissolves in water to form an acid

another name for acid anhydride

acidic oxide

examples of acids in real life

ascorbic acid/vitamin c

citric acid

methanoic acid

lactic acid

acetic acid/vinegar

what neutralizes ascorbic acid

sodium hydrogen carbonate

use of citric acid

removes rust stains by helping loosen the stain so it can be washed off

where is methanoic acid found

venom of ants

what neutralizes methanoic acid

sodium hydrogen carbonate

zinc oxide

use of vinegar

food preservative, causes the decay of bacteria/pathogens due to low pH

bases

proton acceptors

react with acids to form salts and water

dissolve in water to produce hydroxide ions

alkali

a base that is soluble in water

true/false: most bases are alkalis

false

properties of bases

• bitter

• corrosive

• pH > 7 (turn red litmus paper blue)

• soapy

• electrolytes (alkalis)

ammonium salt + base

ammonia gas + salt + water

the strength of an acid/base is classified by

the degree of ionization of the compound when it is dissolved in solution

strong acids/bases

ionize fully in water, large concentration of H+/OH- ions

weak acids/bases

ionize partially in water, low concentration of H+/OH- ions

indicators

used to tell how acidic or basic a substance is (i.e. distinguish between an acid and a base), based on the number of H+ ions in a solution

litmus paper

red in acids, blue in bases

methyl orange

red in acids, yellow in bases

screened methyl orange

red in acids, green in bases

phenolphthalein

colourless in acids, pink in bases

classification of oxides

acidic

basic

amphoteric

neutral

acidic oxides

oxides of non-metals and are also known as acid anhydrides, that dissolve in water to form an acid and react with bases to form salt and water

examples of acidic oxides

carbon dioxide, nitrogen dioxide, nitrogen trioxide, sulphur dioxide, sulphur trioxide

basic oxides

the oxides of metals, react with acids to produce salt and water

examples of basic oxides

calcium oxide, lithium oxide, sodium oxide, potassium oxide

amphoteric oxides

oxides of metals that react with both acids and bases to produce a salt and water

examples of amphoteric oxides

lead, aluminium, and zinc oxides/hydroxides

amphoteric oxide + base

salt containing oxygen + water

neutral oxides

react with neither acids nor bases

examples of neutral oxides

carbon monoxide, nitrogen monoxide, dinitrogen monoxide

salt

a compound formed from reacting an acid and a base. occurs when the hydrogen ion in an acid is replaced with the metal/ammonium ion from a base

classification of salts

normal salts

acidic salts

normal salts

formed when all of the hydrogen ions in an acid have been replaced with metal/ammonium ions from a base

which basicity of salt can only form normal salts

monobasic salts

acidic salts

formed when not all of the hydrogen ions in an acid have been replaced with a metal/ammonium ion in a base

which basicity of acid forms acidic salts

dibasic, tribasic

water of crystallization

in hydrated salts, occurs when a set proportion of water molecules are within a fixed position within the crystal

what does water of crystallization affect in the salt

shape

colour

hydrated salt + heat

anhydrous salt

4 methods used to prepare salts

precipitation

direct combination

titration

neutralization

precipitation

insoluble salt using two soluble salts

direct combination

anhydrous chloride using a metal and heated chlorine gas

titration

soluble salt using an acid and a base

neutralization

soluble salt using an acid and an insoluble metal, base or carbonate

method used to prepare sodium, potassium and ammonium salts

titration

general method of preparing a soluble salt

1. Carry out neutralization or titration reaction

2. Filter out excess

3. Gently heat up until crystals begin to form

4. Dry crystals with distillate

salts used in baking

sodium hydrogen carbonate

how sodium hydrogen carbonate works in baking

neutralizes the ethanoic acid to produce carbon dioxide, causing a rise in bread, cakes, etc.

salts used as food preservatives

sodium nitrate

sodium nitrate

sodium chloride

sodium benzoate

sodium nitrate/nitrite

preserve meats in particular by preventing the growth of bacteria, slow the oxidation of fats and oils also increasing their flavor

sodium chloride

preserves meats and fish, used with sodium nitrate/nitrite

sodium benzoate

preserves foods with low pH like fruit/lemon juice by reducing it preventing growth of microorganisms

calcium carbonate salts are used for

manufacturing cement

calcium sulphate salts are used for

plaster of paris

magnesium sulphate salts are used for

health benefits, plant growth

dangers of sodium benzoate and nitrate/nitrite

carcinogenic

lead to defects in kids — asthma, brain damage, hyperactivity

dangers of sodium chloride

hypertension

neutralization

an exothermic reaction in which an acid and a base react to form a salt and water, produce a pH of 7

neutralization point

also known as the end point. occurs when all the hydroxide ions in a solution have reacted with the hydrogen ions

to determine the neutralization point

indicator

titration

2 types of titration

thermometric

volumetric

thermometric titration

involves reacting an acid and a base while monitoring the heat change of the reaction. the peak temperature is the temperature at which the solution was neutralized

volumetric titration

involves slowly reacting an acid and a base using an indicator, when the indicator changes colour the amount of acid/base that has been used is the amount that causes the neutralization point

types of neutralization reactions in everyday life

• fluoride replacing hydroxide in the teeth to prevent them from decay

• CaOH and NH4 being placed in the soil at the same time, no nutritional benefits as all useful ions are gone, ammonia produced

• antacids (sodium hydrogen carbonate)

antacids

used to treat acid reflux and indigestion— neutralize the excess acid in the stomach

use of titration

to determine molar/mass concentration

to determine molar ratio

to create a salt

to create a standardize solution

using titration to determine molar ratio

1. Find the moles of both substances

2. Divide the smaller by the larger one

using titration to determine the molar/mass conc

1. Write out the equation

2. Determine the molar ratio

3. Find the amount of moles of each

4. Determine molar/mass conc

instruments involved in titration

pipette, burette, beaker, conical flask, filter funnel, retort stand, volumetric flask

standard solutions are created in a

volumetric flask

titrant

solution whose volume is known

analyte

solution whose volume is to be determined

formula linking molarity and volume of two substances

M1 x V1 = M2 x V2

equivalence point

the point at which all of an acid has reacted with all of a base

end point

the point at which the colour of an indicator/temperature changes during a titration

how to calculate theoretical yield

1. write out balanced equation

2. calculate moles of given substance

3. look at molar ratio

4. use molar ratio to find mass of other substance