Revision for salt, electrochemistry, carbon compounds , thermochemistry
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The document discusses several chemical formulas, equations, and calculations including the heat of precipitation of barium sulfate from a mixture of potassium sulfate and barium chloride solutions. It also addresses the properties and production of natural rubber from latex and how treating rubber with sulfur through the process of vulcanization improves its properties for uses such as in tires and gloves.
![d. Calculate
i. The heat released in the
experiment. [Specific heat capacity
of water = 4.2 Jg-1oC-1, Density of water
= 1.0 g cm-3]
Heat release
= mc
=100x4.2x(34.5- 29.5)J
= 2100J 2m](https://image.slidesharecdn.com/revisionforselaras2-fromselaras1form5sem1selaras22012-120416052840-phpapp02/85/Revision-for-salt-electrochemistry-carbon-compounds-thermochemistry-35-320.jpg)
Revision for salt, electrochemistry, carbon compounds , thermochemistry
- 1. SELARAS 2 FORM 5 2011
- 2. Question 1 b) Write the formula of the following substances: • Hydrochloric acid – HCl • Sulphuric acid – H2SO4 • Barium hydroxide – Ba(OH)2 • Barium sulphate – BaSO 4
- 3. b) Hydrochloric acid is a strong acid. Why? HCl ionised completely in water to produce high concentration of hydrogen ion
- 4. c)Silver chloride and copper (II)sulphate are two salts that are required to be prepared in the lab i) Which one is the soluble salt? Copper (II) sulphate ii) State the name of acid needed to prepare copper (II) sulphate Sulphuric acid
- 5. iii) Silver chloride is prepared by the precipitation method.Write the chemical Equation to prepare silver chloride salt AgNO3 + NaCl → AgCl + NaNO3
- 6. d) Calculate the following: i) What is the concentration of 50 cm3 NaOH solution needed to neutralise 100 cm3 0.5 moldm-3 H2SO4? 2 NaOH + H 2 SO4 → Na2 SO4 + 2 H 2O Where M 1V1 M 2V2 = M1 = molarity of acid V1 = volume of acid a b M2 = Molarity of alkali V2 = volume of alkali a = no. of mol of acid in the equatn b = no. of mol of alkali in the equatn
- 7. 2 NaOH + H 2 SO4 → Na2 SO4 + 2 H 2O M 1V1 M 2V2 Where = M1 = molarity of acid a b V1 = volume of acid 0.5 x100 M 2 x50 M2 = Molarity of alkali = V2 = volume of alkali 1 2 a = no. of mol of acid in the equatn M 2 = 0.5 x100 x 2 / 50 b = no. of mol of alkali −3 in the equatn M NaOH = 2moldm
- 8. i) How much water is needed to form a solution of 1.0moldm-3 NaOH solution from a solution of 50cm3 sodium hydroxide 2.0moldm-3 Where M 1V1 = M 2V2 M1 = molarity of original 2(50) = 1(V2 ) solution V1 = volume of original V2 = 100 solution M2 = Molarity of diluted ∴VolumeH 2O = solution V2 = total volume of 100 − 50 = 50cm 3 diluted solution
- 9. 2.Diagram 2 shows the apparatus set up for two types of cells, P and Q
- 10. a) State one difference in energy change between cell P and cell Q: In cell P energy change is from electrical energy to chemical energy In cell Q energy change is from chemical energy to electrical energy
- 11. b) What is the product at the anode in cell P? Oxygen gas c) Write the half equation for the discharge of cation in cell P 2+ − Cu + 2e → Cu
- 12. d) State one observation at electrode zinc in cell Q Zinc electrode becomes thinner
- 13. e) Diagram 2.2 shows the apparatus set-up for the electrolysis of sodium chloride solution using carbon electrodes
- 14. i) State all ions attracted towards electrode P and Q Electrode P Electrode Q Na , H + + Cl , OH - - ii) State which ion discharge at electrode Q. Explain why Chloride ion because the concentration of Cl- is higher than concentration of OH-
- 15. iii) Describe one chemical test to identify gas X Place burning wooden splinter into mouth of test tube, ‘pop’ sound will be produced
- 16. Diagram 3 shows a series of reaction of compound P. Compound P and compound Q are shown in condensed structural formulae.
- 17. Compound Q CO2 + H2O CH3CH2 CH3 Combustion I II Compound P Compound R Steam and CH2=CHCH3 Phosphoric acid + Ethanoic acid III + concentrated sulphuric acid Compound S Diagram 3
- 18. (a) Compound P is propene . State the homologous series of compound P ALKENE
- 19. (b)Compound Q is used as a cooking gas. • i) State the molecular formula of compound Q C3H8 ii) Write a chemical equation for the combustion of compound Q to produce carbon dioxide and water C3H8 + 5O2 3CO2 + 4H2O
- 20. (C) Compound P can be changed to compound R which is an alcohol through process II. • Name process II HYDRATION • State the general formula for alcohol CnH2n+1OH
- 21. (d) Explain briefly how compound S can be prepared from compound R in laboratory. In your answer include the appropriate reagents and condition for the preparation.
- 22. • Add absolute propanol and glacial ethanoic acid into a beaker. • Add slowly concentrated H2SO4. • Heat under reflux for 6 hours • Distill the mixture to get the products.
- 23. e) An organic compound W has a molecular formula of C4 H8 . Compound W has 3 isomers. Draw two structural formulae of two isomers of W.
- 24. e) isomers of W.
- 25. 4) Natural rubber is a polymer, where the monomer is isoprene or 2- methylbuta-1,3- diene. Natural rubber is obtained from latex, which is a colloid made up of rubber particles and water. Draw Structural formula of isoprene (1m)
- 26. Draw labelled diagram of latex particle in water (2m)
- 27. Explain why latex in the original form does not coagulate
- 28. However when latex is exposed to air or when acid is added, coagulation of latex occur. Explain(3m) • Air contains bacteria that acts on latex to produce lactic acid
- 29. The properties of natural rubber can be improved by treating it with sulphur. Name this process (1m) VULCANISATION
- 30. State ONE use of the treated rubber above (1m) TYRE GLOVE RUBBER HOSE
- 31. QUESTION 5 Initial temperature of both solutions = 29.5 o C Highest temp of the 50 cm3 of 1.0 mol mixture = 34.5 o C dm-3 Potassium sulphate solution 50 cm3 of 1.0 mol dm-3 Barium Chloride solution
- 32. a. What is meant by the heat of precipitation of barium sulphate? • Heat change when 1 mole of barium sulphate is formed from barium ion and sulphate ion in aqueous solution 1m
- 33. b. Write an ionic equation for the reaction Method: First, write the formula of the precipitate on the right side of the equation Second, write the ions of the precipitate on the left side of equation • Ba 2+ + SO4 -2 BaSO4 1m
- 34. c. State one observation for the experiment • White precipitate forms or the containers become warm 1m
- 35. d. Calculate i. The heat released in the experiment. [Specific heat capacity of water = 4.2 Jg-1oC-1, Density of water = 1.0 g cm-3] Heat release = mc =100x4.2x(34.5- 29.5)J = 2100J 2m
- 36. ii. The number of moles of barium sulphate formed • Mole of BaSO4 = MV/1000 = 50 x 1.0 /1000 = 0.05 1m
- 37. iii. The heat of precipitation of barium sulphate 0.05 mole BaSO4 produce heat 2100 J 1 mole BaSO4 2100 / 0.05 J = 42000 J ∆ H = - 42 kJ mol-1
- 38. e.Draw the energy level diagram for the precipitation of barium sulphate Energy Ba + SO 4 2+ -2 ∆ H = -42 kJ mol-1 BaSO 4 2m