Chapter 14 Chemicals for Consumers


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Chapter 14 Chemicals for Consumers

  1. 1. Rossita Radzak SASER CHEMICALS FOR CONSUMERS 1. (a) A student washed his socks which had oily stains. Explain the cleansing action of soap on the oily stains.  In water soap ionizes to form ions/anion CH3(CH2)x COO- and cation, sodium ions, Na+  The anions consists of hydrophilic part ( -COO -) and hydrophobic part (hydrocarbon)  Hydrophilic part dissolve in water only but hydrophobic part dissolve in grease only  The anions reduces surface tension of water, causing wetting of greasy surface.  During washing and scrubbing, the anions pull the grease and lifted it off the surface and break it into a small droplets (Emulsifying agent)  Rinsing away the dirty water removes the grease (the dirt) and excess soap and the surface is clean. Preparation of soap Procedure 1. pour 10 cm3 palm oil ( vegetable oil ) into a beaker 2. add 50 cm3 of 5.0 mol dm-3 NaOH / KOH solution 3. heat the mixture for (10 minutes) 4. stir 5. stop heating 6. add 50 cm3 distilled water and solid NaCl 7. boil the mixture for 5 minutes 8. cool 9. filter 10. wash / rinse 11. dry ( press the residue between filter papers Test 12. place a small amount of the residue into a test tube add distilled water, shake it well. produce a lot of lather ( very foamy) Observation : white solid, slippery and produce a lot of lather ( very foamy). (b) Another student carried out four experiments to investigate the cleansing effect of soap and detergent on oily stains in soft water and hard water respectively. 1
  2. 2. Rossita Radzak SASER Compare the cleansing effect between (i) Experiments I and II (ii) Experiment II and IV Explain the differences in the observation Exp. I and II  The oily stain disappears in Experiment I but remains oily in Experiment II.  Hard water contains Ca2+ and Mg2+ ions which reacts with soap ions to form scum (insoluble salt)  The formation of scum makes anions less efficient for cleaning the oily stain on the sock  In soft water, all anions are used to clean the oily stain  Thus, soap is only effective as a cleansing agent in soft water and ineffective in hard water. Exp. II and IV  The sock in Experiment II remains oily but is clean in experiment IV.  The soap anions form scum when reacts with Ca2+ and Mg2+ ions in hard water.  The formation of scum makes anions less efficient for cleaning  The detergent anions CH3(CH2)x OSO3- / CH3(CH2)x SO3- do not form a 2+ 2+ O precipitate with Ca and Mg in hard water.  Hence, detergent cleans effectively in hard water but soap does not clean effectively in hard water. 2
  3. 3. Rossita Radzak SASER Compare and contrast soap and detergent Soap Detergent CH3 (CH2)15 COO- Na+ Sodium carboxylate Sodium alkyl sulphate Sodium alkylbenzene sulphonate Material : fat, Petroleum fractions : long chain Petroleum fractions : long chain vegetable oil, NaOH alcohol, NaOH / KOH, alkene, NaOH / KOH, / KOH, mol dm-3 5 mol dm-3 , H2SO4 5 mol dm-3, H2SO4 Preparation Preparation Preparation Saponification 1. sulphonation 1. alkylation 2. neutralization 2. sulphonation 3. neutralization Food additive Type Function Examples Preservatives To slow down/ prevent the Salts/sugar: draws the water out of the cells growth of microorganism, of microorganism and retards the growth of therefore food can kept for longer microorganism periods of time Vinegar: provides an acidic condition that inhibits the growth of microorganism. NaNO3 (Burger) Benzoic acid / sodium benzoate: to slow down the growth of microorganism Antioxidants To prevent oxidation that can Ascorbic acid and vitamin E (Tocopherol) causes rancid fats and brown fruits Flavourings To improve the taste of food and Sugar , salt, MSG, vinegar, aspartame and restore taste loss because of synthetic essences (ester) processing Stabilizers To prevent emulsion from Lecithin, fatty acid separating out. Thickeners Its use to thicken foods Pectin, acacia gum, gelatine Dyes To add or restore the colour in Natural dyes and artificial dyes: Azo food in order to enhance its compounds or triphenyl compound. visual appeal and match consumers expectations. 3
  4. 4. Rossita Radzak SASER Medicine Type Function Example Effect on health Analgesic To relieve pain without Aspirin  -Internal bleeding affected consciousness and ulceration -can cause brain and liver damage to children Paracetamol  Over dose can cause brain and liver Codeine  damage Addiction, depression and nausea Antibiotics To treat infections cause by Penicillin, bacteria (tuberculosis, TB). streptomycin Can kill or slow down the growth of bacteria. Psychotherapeutic To alter the abnormal thinking, feelings and -High dose can lead behaviors. Divide into 3 to anxiety, categories : -amphetamine  hallucinations, severe a) stimulant: to reduce depression, and fatigue  psychological dependence. b) antidepressant: -barbiturate / to reduce tension and tranquilizer  Overdose can lead to anxiety  respiratory difficulties, -chlorpromazine  sleeplessness, come, -haloperidol, death. c) antipsychotic: to treat  clozapine -dizziness, psychiatric illness drowsiness, rapid heartbeat. 4
  5. 5. Rossita Radzak SASER The additives in detergent Type Function Example Fragrances To add fragrance to both the detergent and fabrics Biological enzymes To remove protein stains such as blood Amylases, proteases, celluloses, lipases Whitening agents To convert stains into colourless Sodium perborate substances Suspension agents To prevent the dirt particles removed Carboxymethylcellulose from redepositing onto cleaned fabrics (CMC) Fillers To add to the bulk of the detergent and Sodium sulphate, sodium enable it to be pour easily silicate Optical whitening To add brightness and whiteness to Fluorescent dyes white fabrics. Builder To enhance the cleaning efficiency of Sodium tripolyphosphate detergent by softening the water 5