School Science Lessons
2025-01-11
Chemistry, Aa to Ac
Please send comments to: j.elfick@uq.edu.au
Contents
AAS Atomic Absorption Spectroscopy
Abbreviations Chemistry
Abbreviations English language
Absolute zero, Kelvin scale
Absorption spectrum, Sodium, (Experiment)
Abietic acid
Abscisic acid
Absinthin
Absolute alcohol ethanol, (Experiments)
Absolute zero Kelvin scale
Abuse of volatile substances
Acacetin
Acanthicifoline
Acanthosides
Acaricides, (Agriculture)
Accumulator, Lead accumulator cell, (Experiments)
Accuracy and error, Errors
Acerosin
Acephate
Acesulfame
Acetal
Acetaldehyde, (Experiments)
Acetates, Ethanoates, (Experiments)
Acetyl group, −COCH3, −C(=O)−CH3, Ac, ethanoyl
Acetylharpagide
Acetamide, (Experiments)
Acetaminophen, Paracetamol, (Experiment)
Acetamiprid, Neonicotinoid insecticide
Acetic acid, Ethanoic acid, (Experiments)
Acetic alcohol, Prepare, (Experiment)
Acetic anhydride, Prepare
Aceto-alcohol, Prepare
Aceto-carmine, Prepare
Aceto-orcein, Prepare
Acetoacetic acid, (Experiment)
Acetochlor, (Agriculture)
Acetone, (Experiments)
Acetone peroxide, TATP
Acetonitrile
Acetosyringone
Acetyl chloride
Acetyl eugenol, Eugenol acetate
Acetylcholine
Acetylides
Acetyldigoxin
Acetylene, (ethyne), (Experiments)
Acetylpyrrolidine,
Acetylpyrroline
Acetylsalicyclic acid, Aspirin, (Experiments)
Achillin
Acid-base indicators, (Experiments)
Acid acid-, acids, acidic, acidify, (Experiments)
Acid anhydrides
Acid fuchsin, (Prepare)
Acid rain
Acidity, (Experiments)
Acolongifloroside K
Aconine
Aconitine
Acridine
Acriflavine
Acrilan (trade name)
Acroleic acid
Acrolein
Acronidine
Acryl polymer (Experiments)
Acrylamide
Acrylates
Acrylic acid propenoic acid, (Experiment)
Acrylic glass Polymethyl methacrylate, (Experiments)
"Acrylics"
Acrylonitrile (Experiments)
Actinides, actinoids
Actinidine
Actinium, Ac
Actinolite, (Geology)
Activated carbon activated charcoal
Active constituent (Pesticides label)
Activity series of metals as reducing agents
Acute toxicity
Acyclic hydrocarbons
Acyl halide
Abbreviations
i.e. (id est) means "that is" or "in other words".
e.g. (exempli gratia) means "for example".
viz. (videlicet) means "namely" or "that is to say".
et al. (et alii) means "and others" or "and collaborators".
q.v. (quod vide) means "which to see", written after words to be looked up in the current document.
ibid. (ibidem) means "in the same place", refers to a previously listed work.
cf. (confer) means to see a given citation for comparison.
Acerosin
Acerosin, C18H16O8, is a trimethoxyflavone metabolite.
It occurs in Scoparia dulcis, Iva acerosa, Helianthus, Gardenia, Vitex, and in peel of mandarin orange Citrus reticulata.
Acesulfame
Acesulfame, C4H5NO4S is a sulfamate ester, irritant, sweetening agent, and environmental contaminant.
Food code E950, Acesulphame Potassium, Acesulfame-K, Ace-K, C4H4KNO4S, synthetic chemical, artificial sweetener, Health risk, tumours
Food code E962, salt of aspartame-acesulfame, artificial sweetener, emulsifier, stabilizer, thickener and gelling agent, Health risk, tumours
19.6.3 Cola, Diet or Light contents
Acetaldehyde
Acetaldehyde C2H4O, C2H4O, CH3CHO, ethanal, is a colourless liquid, choking odour, BP 21°C, vapour irritates eyes, tobacco smoke carcinogen.
16.3.2.7 Ethanal with potassium dichromate, Prepare
16.3.2.6 Ethanal with potassium manganate (VII), Prepare
Acetamide
Acetamide, CH3CONH2, C2H5NO, ethanamide, acetic acid amide, colourless crystals, mouse odour, low toxicity, skin irritation.
It is formed from condensation of acetic acid with ammonia, and it is used as solvent.
Amide RCONH2, (amine + acid), No prefix
Suffix, -oic, Suffix, -amide, e.g. acetamide = ethanamide, CH3CONH2
16.1.5.6 Amides
24.7.3 Heat energy changes solid to liquid
24.7.5 Latent heat of fusion of ice to water
Acetates
Acetates CH3COO-, Ethanoates
An acetate (ethanoate) is a salt or ester of acetic acid (ethanoic acid).
An acetate as a salt: Sodium acetate (sodium ethanoate), CH3COONa.
An acetate as an ester: Ethyl acetate, (ethyl ethanoate), CH3COO(C2H5).
If acetate is shown as OAc−, acetic acid is shown as HOAc.
Weak acids, e.g. ethanoic acid (acetic acid, CH3COOH, carbonic acid and sulfurous acid dissociate little in aqueous solution.
However, their salts, e.g. potassium acetate CH3COOK are completely dissociated into ions.
Acetic anhydride (CH3CO)2O
3.5.7 Celluloid
3.5.8 Cellulose acetate, Cellulose triacetate
Experiments
12.3.9 Acids with salts
16.4.2 Ethyl acetate, Prepare
17.3.5 Ethyl acetate with sodium hydroxide, autocatalyctic hydrolysis
Acanthosides
Acanthoside B, Eleutheroside e1, C28H36O13, syringaresinol beta-D-glucoside
It occurs in Eucommia ulmoides bark, in Acanthopanax sessiliflorus roots
Acanthoside D, Syringaresinol-di-O-glucoside, Liriodendrin, C34H46O18, beta-D-glucoside, antioxidant, anti-inflammatory
It occurs in Acanthopanax sessiliflorus roots, Eleutherococcus senticosus, Liriodendron bark, Penstemon.
Acetic anhydride
Acetic anhydride, (CH3CO)2O, ethanoic anhydride, acetic acid anhydride, acetyl oxide, acetic oxide,
Use < 25 mL or g in a fume cupboard or a well-ventilated area
Solution < 8%, Not hazardous, i.e. 8% acetic acid
It is a highly volatile liquid, irritating odour, reacts with moisture in air, corrosive to skin, strong respiratory irritant.
(CH3CO)2O + H2O --> 2 CH3COOH
acetic anhydride + water --> acetic acid
You can prepare acetate esters from alcohols by reaction with acetic anhydride.
Reactions with alcohols, oxides, permanganates, nitric acid may be hazardous to explosive. Be careful!
Acetoacetic acid
Acetoacetic acid, C4H6O3, CH3COCH2COOH, 3-oxobutanoic acid, is a fatty acid
It occurs in Phaseolus vulgaris, and Apium graveolense.
16.1.9 Ethyl acetoactonate
16.3.3 Keto acids
19.5.1Tests for ketones
Acetone
Acetone, CH3COCH3, 2-propanone, propanone, dimethyl ketone, is highly flammable, characteristic irritant vapour, slightly toxic if ingested
Use low cost, technical grade acetone, from hardware store, as solvent, and to clean glassware.
Acetone ACS reagent, 99.5%, clear colourless volatile liquid, characteristic smell, inflammable
RD 0.79 gm cm-3, BP 56.5oC, miscible with water and ether, and oils sharp sweet taste
Acetone is a curing agent for epoxy resin adhesives, surface coating, irritant.
Use acetone in a fume cupboard or use < 50 mL in a well-ventilated area.
Acetone react violently with chloroform.
Use ethyl acetate or methyl isobutyl ketone as alternative solvent to acetone.
Heat acetone on a water bath, NOTon a naked flame.
Acetone dissolves polystyrene packing pieces rapidly by dissolving the linking units.
Common names, Nail polish remover, (but not in Australia), e.g. "Cutex", nail paint remover, paint thinner, may be sold as "pure acetone".
Junior secondary students should use acetone only as a cold solvent, and they should NOTreact or heat acetone.
2.3.7 Cleaning agents, solvents
3.1.2 Boiling point of inflammable liquids
12.19.9.7 Bromination of acetone
15.4.16 Potassium dichromate as an oxidizing agent, (See: 5.)
Experiments
10.12.0 Separate by solvent extraction of oil from peanuts
17.3.7 Oxidation of acetone vapour, copper catalyst
Acetonitrile
See diagram Acetonitrile
Acetonitrile, CH3CN, (acetonitrilo), cyanomethane, methyl cyanide, flammable, colourless liquid, sweet ether-like odour, simplest organic nitrile
It is toxic if ingested.
Acetonitrile, Solution < 3%, Not hazardous
Acronitrile is used in C3H3N acrylics (plastics), vinyl cyanide, cyanoethylene, synthetics, paint.
Indole-3-acetonitrile C10H8N2
Acetosyringone
Acetosyringone, C10H12O4, is a phenol, irritant, non-steroidal anti-inflammatory drug, anti-asthmatic drug, and an non-narcotic analgesic.
It occurs in Justicia adhatoda, Polyporus umbellatus, in Saccharomyces cerevisiae.
It occurs in Nicotiana tabacum root cultures, exuded from roots, to cause infection by Agrobacterium tumefaciens.
Acetoxychavicol acetate
Acetoxychavicol acetate, C13H14O4, is a galangal acetate, an acetate ester, a phenylpropanoid, and an antineoplastic agent.
It occurs in herbs and spices, sweet flag, Acorus calamus, Alpinia galanga, and in Apis cerana.
Snap ginger, (Alpinia calcarata)
Acetoxyeugenol acetate
Acetoxyeugenol acetate, C14H16O5, is a phenylpropanoid, a monomethoxybenzene
It occurs in Alpinia galanga.
Snap ginger, (Alpinia calcarata)
Acetylbrowniine
Acetylbrowniine, C27H43NO8, 14-O-Acetylbrowniine, is an acetate ester obtained by acetylation of browniine, C25H41NO7.
Acetyl chloride
Acetyl chloride, C2H3ClO, CH3COCl, C2ClH3O, ethanoyl chloride, acyl chloride, acetic chloride, has low flash point.
It is toxic by all routes, colourless, fuming liquid, pungent odour, vapour heavier than air, irritates eyes and mucous membranes, and corrodes metals.
Acetylcholine
Acetylcholine C7H16NO2+, is a neurotransmitter stimulates muscle, acetyl ester of choline, major transmitter at neuromuscular junctions.
It occurs in fruit and seed of breadfruit.
9.0, Fruit and seed, (See: 4. Acetylcholine)
Atropine C17H23NO3, alkaloid
Nicotine C10H14N2, alkaloid
Acetylharpagide
Acetylharpagide, C17H26O11, 8-O-Acetylharpagide, iridoid glucoside, ecdysteroid,
It is a Chinese medicine, anti-inflammatory, vasoconstrictor, antibacterial, antiviral, acts on smooth. muscle, inhibits, Epstein-Barr virus (EBV),
It occurs in Ajuga decumbens, and Ajuga reptans
Acetylpyrrolidine
Acetylpyrrolidine, C6H11NO, 2-Acetylpyrrolidine
Substituted pyrrolidine, CH3COC5H4N, occurs in malt, popcorn, and beer
Acetylpyrroline
Acetylpyrroline, C6H9NO, 2-Acetyl-1-pyrroline (2AP), is in white bread smell in cereals, hot popcorn, jasmati and basmati rice, wheat bread crust, sweet corn
It occurs in Screwpine.
Acids
Acid acids, acidic, acidify, acidity
Acid-base indicators
19.1.1 Acid-base indicators in the home
12.11.4.1 Acid-base neutralization, acid with baseforms a saltand water
12.2.1 Acid-base reactions
16.1.5.7 Acid anhydrides
12.3.15 Acid dissociation constant at logarithmic scale, pKa
1.0.0 Acid fuchsin indicator, Andrade's
Acid rain
12.3.0 Acids, Chemical reactions
19.1.5 Acids in foods, Food acids
1.1 Acids, List of mineral acids
1.2 Acids, List of organic acids
Acids with other substances
Acidic oxides (Experiments)
Acidity
19.1.2 Acidulated water, Cooking
3.9.0 Carbonic acid, soda water
12.3.5 Concentrated acids, with a non-metal, carbon
12.3.10 Concentrated acids, with metals, sulfuric acid with copper
12.4.0 Dilute acids with
Prepare acids
12.3.1 Properties of acids
12.16.5 Reactions of sulfuric acid
19.1.17 Solid acids, solubility
12.3.17 Tastes of acids
12.11.2 Tests for acid radicals in solution
12.3.17 Taste of acids, solid acids in the home
12.11.2 Tests for acid radicals in solution
Titration
Acidity
Acidity, definition, [degree of being an acid]
18.1.0.1 Acidity and alkalinity
12.11.4.2 Acidity of vinegar and wine
19.1.1 Acidity regulators, food additives
16.1.5 Acidity test, (milk testing)
6.1.0 Soil acidity
Prepare acids
5.6.4 Prepare acid-base indicators
3.1 Prepare acid alcohol solution
11.0 Prepare acids and bases, dilution instruction
5.4.7 Prepare dilute acids
3.4.10 Prepare dilute acids and bases, (Safety instructions)
Boric acid, Boracic acid, H3BO3
Hydroiodic acid, a strong acid
Hydrochloric acid, HCl
Hydrofluoric acid, HF
Nitric acid, HNO3
Nitrous acid, HNO2
Phosphoric acid, H3PO4
19.1.17 Solid acids, solubility
19.1.11 pH of solid acids
19.1.16 Solid acids, add sodium carbonate
19.1.17 Solid acids, solubility
Citric acid
Tartaric acid
Boric acid
Acid rain
12.8.11 Acid rain and nitrogen oxides, NOx
12.6.0.1 Acid rain, SOx, from burning sulfur or sulfur compounds
18.6.0 Air pollution
12.19.5.0 CFCs, chlorofluorocarbons, "Freons"
Acidic oxides
An acidic oxide is oxide of a nonmetal, e.g. carbon dioxide, or a metal in high oxidation state, e.g. chromium trioxide, CrO3
Acidic oxides do not react with acids.
Acidic oxides form when a nonmetal burns.
Acidic oxides are usually gases at room temperature, e.g. CO2, NO2, SO2, SO3.
Acidic oxide + base --> salt + water
CO2 (g) + NaOH (aq) --> Na2CO3 (s) + H2O (l)
Acidic anhydride is an acidic oxide which reacts with water to form a base.
CO2 + H2O --> H2CO3 (carbonic acid)
SO3 (g) + H2O --> H2SO4 (aq) (sulfuric acid)
Acidic oxides
Carbon dioxide acidic oxides, (non-metal oxides)
Carbon dioxide with barium hydroxide solution
Carbon dioxide with sodium hydroxide solution
Reactions of oxides
Acids with other substances
12.3.4 Acids with aluminiums
12.1.18 Acids with baking soda
12.1.25 Acids with sodium carbonate
12.1.40 Acids with sodium thiosulfate
12.14.18Acids with zinc
12.3.12 Concentrated acids with metals, nitric acid with copper
12.3.14 Concentrated acids with a non-metals, carbon
12.4.0 Dilute acids with
12.3.15 Dilute acids with salts
Acridine
Acridine, C13H9N, toxic if ingested and skin contact, give First aid if ingested: Give water, and induce vomiting
Acridine orange, C17H19N3, an aminoacridine, hydrochloride salt 'acridine orange', is used to stain cell nuclei, e.g. DNA.
See diagram Acridine, (9-Azaanthracene), (2,3-Benzoquinoline)
Acriflavine
Acriflavine, C14H14ClN3, orange-brown, dye and antiseptic
It shows green fluorescence when diluted in water.
Acroleic acid
Acroleic acid, CH2CHCO2H, C3H4O2, acrylic acid, propenoic acid, prop-2-enoic acid, Toxic
It is the simplest unsaturated carboxylic acid.
Acroleic acid, Solution < 5%, Not hazardous,
Corrosive, colourless liquid with an acrid odour
It is used in polishes, paints, coatings, rug backings, adhesives, plastics, textiles, and paper
Polyacrylic acid, cross-linked sodium salt
Polyacrylic acid, water-soluble polyelectrolyte, is used to increase building substances viscosity
Polyacrylamide powder, superabsorbent, is used to make toy product "Instant Wet Expanding Snow"
Sodium polyacrylate, (C3H3NaO2)n, waterlock, is sold as toy product "Super Expanding Creatures"
Sodium polyacrylate gels ghost crystals, Prepare
Acrolein
Acrolein, CH2CHCHO, CH2=CHCHO, C3H4O, acrylaldehyde, 2-Propenal, ethylene aldehyde, acrylic aldehyde, aqualin, Magnacid, Toxic by all routes
It is the simplest unsaturated aldehyde, colourless or yellow liquid, toxic chemical
It has a horrible odour like the smell of burnt fat when glycerol breaks down into acrolein.
Acrolein test for presence of fats: Heat sample with potassium bisulfate --> acrolein released
Acrolein, Solution < 0.1%, Not hazardous, clear, yellowish liquid, sweet, pungent burnt fat smell, highly flammable, volatile organic compound, unstable
It polymerizes in the presence of light or alkali, or strong acids.
It occurs in cigarette smoke and vehicle exhaust, aquatic herbicide, kill algae and waterweeds, and it is used as a pesticide.
Acrylates
Acrylates, CH2=CHCOO−, prop-2-enoates, salts or esters or bases of acrylic acid
Esters of acrylic acid are commonly called acrylates, e.g. methyl acrylate, CH2=CHCOOCH3
Mixture of acrylates, acrylate polymer, is a viscous liquid used as thickener in personal products
Acrylic acid
Acrylic acid, CH2CHCOOH, C3H4O2, CH2=CHCOOH, 2-Propenoic acid, colourless liquid, distinct acrid odour, corrosive to metals and tissue
If heated in a closed container, a violent rupture may occur.
Acrylic acid, CH2CHCOOH, "acrylics"
Butter butter oil, clarified butter, ghee, (See, 6.)
12.5.11, Tests for glycerol
Acrylonitrile
Acrylonitrile, CH2=CH-CN, flammable, low flashpoint, below 32 oC, poison, used to manufacture acrylic acid
Acryl polymer, generic name for fibres > 85% acrylonitrile units
ABS mixed polymer, acrylonitrile, butadiene, styrene, thermoset plastics:
3.7.28 Polypropenonitrile
16.7.6, Nitriles
Acrylonitrile-butadiene-styrene burning test for synthetic fibres
Chewing gum (Tg)
Actinium Ac
Actinium Table of Elements
Actinium RSC
Actinium, Ac, (Greek actinray), refers to light causing chemical change, radioactive, no commercial use.
White radioactive metal, emits a pale blue light, forms coating of actinium oxide to prevent further chemcal reactions
Traces of isotope 227Ac are found in uranium and thorium ores.
12.3.0H Properties of acids
Acids are good electrolytes, react with active metals, turn blue litmus red, and have a sour taste.
Dilute acids contain hydrogen ions in aqueous solution.
You can represent the hydrogen ion, which is really a proton, in different ways to show how it is related to the water molecules in the solution.
You can show it as the hydrated hydrogen ion, [proton, H+(aq)], or as the hydronium ion [oxonium ion, H3O+(aq)]
However, for convenience, use H+(aq).
Concentrated sulfuric acid exists mainly as H2SO4 molecules.
Hydrochloric acid and nitric acid dissociate into ions even in concentrated solution.
Weak acids, e.g. ethanoic acid, acetic acid, CH3COOH carbonic acid and sulfurous acid dissociate very little in aqueous solution.
However, their salts, e.g. potassium acetate CH3COOK, are completely dissociated into ions.
Using the Bronsted-Lowry definition of acids and bases, an acid donates a proton (H+) to another substance and a base accepts a proton from another substance.
When sulfuric acid dissociates in water it donates a proton (H+) to the water molecule.
So in this reaction the water molecule acts as a base.
H2SO4 + H2O --> HSO4-+ H3O+
When ammonia dissolves in water, ammonia accepts a proton and so it is the base.
So in this reaction the water molecule acts as an acid
NH3 + H2O < --> NH4++ OH-
12.3.0.1 Amphoteric substances can act as an acid or a base.
In the above reactions water is acting as a base with sulfuric acid and is acting as an acid with ammonia.
Similarly, bicarbonate ion can act as an acid to donate a proton to form the carbonate ion.
HCO3-+ H2O < --> CO32-+ H3O+
Also, bicarbonate ion can act as a base to accept a proton to form carbonic acid.
HCO3-+ H2O < --> H2CO3 + OH-
12.3.0.2 Polyprotic acids can donate more than one proton, e.g. carbonic acid.
H2CO3 + H2O < --> HCO3-+ H3O+ (The first proton to be donated to a water molecule.)
HCO3-+ H2O < --> CO32-+ H3O+ (The second proton to be donated to a water molecule.)
12.3.0.3 Strong acids and weak acids
A strong acid completely dissociates into ions, e.g. nitric acid has almost complete dissociation, 93%.
HNO3 (aq) + H2O H3O+(aq) + NO3-(aq)
A weak acid only partly dissociates into ions, e.g. acetic acid.
CH3COOH + H2O < --> CH3COO-+ H3O+
Describing acids and bases as strong or weak only refers to their reaction with water and not the concentration or the number of moles in a volume.
The strong acids include:
Perchloric acid HClO4, hydrochloric acid HCl, hydrobromic acid HBr, hydroiodic acid (hydriodic acid), HI, nitric acid HNO3, and sulfuric acid H2SO4.
Any other acid is a weak acid, because it does not completely dissociate in water.
12.3.0.3a Acid dissociation constant
The acid dissociation constant, Ka of the acid HB,
HB (aq) <--> H+(aq) + B-(aq)
Ka = [H+][B-] / [HB]
Ka is a measure of the degree to which an acid or base will dissociate in water.
Stronger acids have a larger Ka and a smaller pKa than weaker acids.
The greater the value of Ka, the more the formation of H+ is favoured, and the lower the pH of the solution.
12.3.0.3b Acid dissociation constant at logarithmic scale, pKa
pKa = -log10Ka
Strong acids have pKa value < −2.
When the pH of solution is at the value of pKa for a dissolved acid, that acid will be 50% dissociated.
Sulfuric acid, H2SO4 --> HSO4-, pKa -10
Hydroiodic acid, HI: HI (g) + H2O (l) --> H3O+(aq) + I-(aq), pKa -9
Hydrobromic acid, HBr: HBr (g) + H2O (l) --> H3O+(aq) + Br-(aq), pKa -8
Perchloric acid, HClO4: HClO4 + H2O --> H3O++ ClO4-, pKa -10
Hydrochloric acid HCl: HCl (g) + H2O (l) --> H3O+(aq) + Cl-(aq), pKa -7
Hydronium ion, H3O+: H2O + H2O < --> H3O++ OH-, pKa -1.74
Nitric acid HNO3: HNO3 + H2O --> H3O++ NO3-, pKa - 1.3
Chloric acid, HClO3, pKa -1.0: Weak acid has pKa value −2 to 12 in water.
Acetic acid, CH3COOH, pKa 4.75
12.3.0.4 pH
Water can transfer a proton from one molecule to another, autionization.
2H2O <--> H3O++ OH-and H2O < --> H++ OH-
The product of hydrogen ion concentration, [H+] and hydroxide ion concentration, [OH-] = the constant, Kw
Kw = [H+] × [OH-] = 1.00 × 10-14
So [H+] = 10-7and [OH-] = 10-7
The hydrogen ion concentration is very small in pure water, so the concentration is describes in terms of its negative log.
pH is the negative log of the hydrogen ion concentration, pH = -log[H+], so hydrogen ion concentration, [H+] = 10-pH.
So acidic solutions have a high [H+] and low pH values.
Basic solutions have low [H+] and high pH values.
A solution that is neither acidic nor basic, a neutral solution, has [H+] = [OH-], so pH = 7.
A more acid solution has pH approaching 1.
A more basic solution has pH approaching 14.
12.3.0.5 Ionization reaction of carbonic acid
H2O (l) --> H+(aq) + OH-(aq)
2H+(aq) + CO32-(aq) < --> H2CO3 (aq) carbonic acid
CO2 + H2O <--> H3O++HCO3-, K1 = 4.4 × 10-7
HCO3-+ H2O <--> H3O++ CO32-, Ka = 4.7 × 10-11
12.3.1 Taste of acids
BE CAREFUL! NEVER TASTE ACIDS IN THE LABORATORY!
Do NOT taste these acids in the laboratory!
Each acid has a sour taste that is a characteristic of acids.
Lemon juice contains the white crystalline citric acid.
Vinegar contains ethanoic acid, acetic acid, CH3COOH.
Experiment
Moisten your finger with a very dilute solution of hydrochloric acid.
Rub your fingers together and then lick them.
Repeat the procedure with very dilute solutions of acetic acid and citric acid.
Do not taste any other acids, because they may damage living tissues.
Citric acid C6H8O7
Acetic acid Ethanoic acid, CH3COOH
12.3.11.1 Nitric acid with metals
Add slowly small pieces of copper, magnesium and zinc to small amounts of dilute nitric acid in separate test-tubes.
If no change is taking place, gently heat the mixture.
Repeat the procedure, 1. with concentrated nitric acid, 2. with concentrated sulfuric acid, and 3. with concentrated hydrochloric acid.
Reactions of metals with nitric acid and conc. sulfuric acid are different from reactions of metals with hydrochloric acid, dilute sulfuric acid and dilute acetic acid.
Copper does not react with dilute acids or with concentrated hydrochloric acid.
Copper does react with dilute and concentrated nitric acids and with hot concentrated sulfuric acid, but does not produce hydrogen gas in reaction with them.
Residual mixtures contain solutions of salts, but writing equations is difficult, because more than one reaction can occur between Cu, Mg, Zn and nitric acid.
For example, when zinc reacts with nitric acid the reaction may produce nitrogen dioxide, nitric oxide, nitrous oxide, zinc nitrate and ammonium nitrate!
12.3.12 Concentrated acids with metals, nitric acid with copper
Nitric acid reacts with metals above platinum in the reactivity series, but does not form hydrogen gas.
BE CAREFUL! DO THIS EXPERIMENT IN A FUME CUPBOARD.
Pour drops of concentrated nitric acid on pieces of copper in a test-tube.
Put a stopper on the test-tube immediately, because brown nitrogen dioxide gas forms.
The nitric acid acts as an oxidizing agent and is reduced to nitrogen dioxide and water.
The reaction is exothermic.
Cu (s) + 4HNO3 (aq) --> Cu(NO3)2 (aq) + 2H2O (l) + 2NO2 (g)
12.3.14 Concentrated acids with a non-metals, carbon
DO NOT DEMONSTRATE THIS EXPERIMENT!
Hot sulfuric acid and nitric acid can react as oxidizing agents with carbon.
Carbon is oxidized to carbon dioxide and nitric acid is reduced to nitrogen dioxide and water.
C (s) + 4HNO3 (aq) --> CO2 (g) + 4NO2 (g) + 2H2O (l)
12.3.15 Dilute acids with salts
1. Add small quantities of sodium chloride, sodium nitrate, sodium sodium sulfite and iron sulfide to about 5 mL of dilute hydrochloric acid in separate test-tubes.
Observe what happens when the mixtures are cold and when they are warmed.
2. Repeat the procedure using dilute sulfuric acid and then concentrated sulfuric acid.
3. Dilute acids do not react with chlorides, nitrates, sulfates, or acetates, unless the metal ions in the salt can form an insoluble salt with the ions in the acid.
4. Acids react with sulfites to produce sulfur dioxide, water and a salt.
5. Acids react with sulfides to produce hydrogen sulfide (rotten egg gas) and a salt.
6. Concentrated sulfuric acid reacts with chlorides to produce hydrogen chloride and a sulfate.
7. Concentrated sulfuric acid reacts with nitrates to produce nitric acid and a sulfate.
8. Concentrated sulfuric acid reacts with s to produce acetic acid and a sulfate.
12.3.16 Acid dissociation constant
Acid dissociation constant, acidity constant, acid-ionization constant
1. The acid dissociation constant, Ka, measures the strength of an acid in solution.
2. An acid, HA, dissociates into A-, conjugate base, and H+, hydrogen ion (proton).
The equilibrium equation when concentrations do not change is, HA < --> A-+ H+.
3. Dissociation refers to the break up of a molecule into smaller molecules, atoms or ions.
In a buffer solution of the salt of a weak acid with a weak acid, the dissociation of the weak acid is negligible, but a salt may be dissociated completely into ions.
4. The dissociation constant, Ka is the equilibrium constant of a reversible dissociation including the ionization reactions of acids and bases in water.
The dissociation constant Ka = [A-] [ H+] / [HA] in mol / litre.
5. However, dissociation is usually expressed as a logarithmic constant, pKa, where pKa = -log10 (1/Ka).
It is the quotient of the equilibrium concentrations, in mol/L for ionization reactions at 25oC.
For pKa, the larger the value the weaker the acid, so strong acids have pKa < 2, and weak acids have pKa >2, < 12.
6. Confusion happens, because both Ka and pKa are sometimes both called "acid dissociation constant"!