Skema sbp paper 2 essay part c no. 9, 10

Essay part c) By using suitable examples, state 2 applications of neutralization in daily life [ 4 marks]

Use ammonia to prevent latex from coagulate 2. Use lime /quick lime (calcium oxide)/ slaked lime (calcium hydroxide), chalk (calcium carbonate) to neutralise acidic soil 3. Use magnesium hydroxide / toothpaste to neutralise acid produced by bacteria in our mouth 4. Use antacid /sodium hydrogen carbonate to neutralise acid in stomach of gastric patients

Any 2 applications ( 4 marks) Rub bee sting or ant stings ( which is acidic)with calcium carbonate Rub wasp sting ( which is alkaline ) with vinegar Any 2 applications ( 4 marks)

b) By using one named example for each alkali, explain why the pH values of the alkalis are different ( 6 marks)

NOTES on pH values and conc of H + ions and OH - ion lower The higher the conc of H+ ion, the ……..the pH value So strong acid has a … … pH value than a weak acid of the same concentration lower higher The higher the conc of OH- ion, the …..the pH value So strong alkali has a ……. pH value than a weak alkali of the same concentration higher

Example of R ; sodium hydroxide solution/ litium hydroxide solution/ potassium hydroxide solution (any strong alkali) R ionised completely in water and produced high concentration of OH- ions Example of Q : ammonia aqueous / solution ( weak alkali) Q ionised partially in water and produce low concentration of OH- ions the higher the concentration of OH – ions in R the higher the pH values

Barium carbonate is insoluble salt Solution X and solution Y are used to prepare barium carbonate salt describe the preparation of barium carbonate salt in the laboratory [ 10 marks] Barium carbonate is insoluble salt

NOTES – soluble and insoluble salts sulphates Chlorides carbonates nitrates PCB, PbSO4, CaSO4, BaSO4 All except PAH, PbCl2, AgCl, HgCl2 All except KAN, K2CO3, Na2CO3, (NH4)2CO3 All except All

Notes on methods to prepare salts Soluble salts Not KAN salts KAN salts Hot acid + excess solid ( metal/metal oxide/metal hydroxide/metal carbonates) method Titration method Insoluble salts Precipitation or double decomposition

State which method to use for the preparation of these salts notes State which method to use for the preparation of these salts Copper(II) sulphate Barium sulphate Hot acid + excess ( copper oxide/ copper(II) hydroxide/ copper(II) carbonate Precipitation Sodium nitrate Titration Silver chloride Zinc chloride Precipitation Hot acid + excess ( zinc/ zinc oxide/ zinc hydroxide/ zinc carbonate Potassium sulphate Titration

notes TO PREPARE SALT SOLUBLE SALT INSOLUBLE SALT KAN SALTS NOT KAN SALTS

solution 1 is barium nitrate solution 50 cm3 of 1 solution 1 is barium nitrate solution 50 cm3 of 1.0 moldm -3 Soln 2 is sodium carbonate solution 50 cm3 of 1.0 moldm -3 Pour solution 1 into a beaker Add solution 2 into the beaker with solution 1 Stir the mixture using glass rod Filter the mixture Rinse the residue with distilled water Dry the residue in between sheet of filter papers to dry

Ba(NO3) 2 + Na2CO3  BaCO3 + 2NaNO3 Equation Ba(NO3) 2 + Na2CO3  BaCO3 + 2NaNO3

10 a) compound A and B burnt completely in oxygen o produce carbon dioxide and water A) name compound B Why Compound B produce more soot [ 4 marks] 1- hexene or hex-1-ene % of C in compound B = 6C/ C6H12 =12x6/ 6(12) + 12(1) = 72/84 = 86% % of C in comp A = 6C/ C6H14 =12x6/ 6(12) + 14(1) = 72/86 = 84% % of C in compound B is more than in compound A

NOTES Physical properties of organic compound Ethane or Ethene Colourless gas , low mp and bp, NOT dissolve in water, NOT conduct electricity

NOTES Physical properties of organic compound Ethanol Colourless liquid Volatile liquid low mp and bp, Miscible in water, NOT conduct electricity

Physical properties of organic compound NOTES Physical properties of organic compound Ethanoic acid Colourless liquid Volatile liquid low mp and bp, dissolve in water, NOT conduct electricity in glacial form, but conduct electricity in aqueous form

Physical properties of organic compound NOTES Physical properties of organic compound Colourless liquid, Sweet smelling low mp and bp, volatile liquid, NOT dissolve in water, NOT conduct electricity Floats on water Less dense than water Ethyl ethanoate

Low melting point and boiling point Does not conduct electricity b) State one physical property of compound K. Describe briefly a chemical test to differentiate between compound J and compound K [ 6 marks] Compound K is ethanol Miscible in water Low melting point and boiling point Does not conduct electricity Volatile colourless liquid

Easy chemical test for carbon compounds notes Add bromine water, brown bromine colour decolourise Alkene Alcohol Carboxylic acid Add acidified K2Cr2O7 and warm Orange colour change to green Add in a few marble chips, pass the gas through lime water, turns milky

J is ethanoic acid K is ethanol Describe briefly a chemical test to differentiate between compound J and compound K [ 6 marks] Pour 2 cm3 of compound J into a test tube Add a few drops of acidified potassium dichromate(VI) solution Warm slowly , Observe colour change Repeat the procedure above with compound K If acidified potassium dichromate solution change from orange to green, then the compound is alcohol J is ethanoic acid K is ethanol

Describe how to prepare an alkene from a named alcohol through dehydration process. In your description, include the diagram of the apparatus set up and balanced chemical equation for the reaction [ 10 marks]

2. Place glass wool in a boiling tube 3. Add a few drops of ethanol to the glass wool 4. Clamp the boiling tube horizontally 5. Place a porcelain chips in the middle of the boiling tube 6. Heat the porcelain chips strongly 7. Heat the ethanol 8. Collect the gas produced in a test tube 9. Equation: C2H5OH → C2H4 + H2O

1) complete sbp – paper 3 – all questions for tomorrow at 10 pagi homework 1) complete sbp – paper 3 – all questions for tomorrow at 10 pagi 2) read up planning experiment- 6 examples with answers 3) read up essay and answers MARA section B and C