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The half equations involved in a cell are:
2H2O(l) + 2e = H2(g) + 2OH-(aq): Eθ = - 0.83V O2(g) + 2H2O(l) + 4e = 4OH-(aq): Eθ = + 0.40V a) Write the overall equation for the electrochemical cell. b) Calculate he e.m.f. generated by a battery consisting of ten cells. c) State one environment advantage of using these cells in spacecrafts.
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The diagram below represents set up for large scale manufacture of hydrochloric acid.
Study it and answer the questions that follow. 
a) Name substance X
b) What is the purpose of the glass beads? c) Give two uses of hydrochloric acid.
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Analysis of a compound showed that it had the following composition: 69.42% carbon, 4.13% hydrogen and the rest oxygen.
a) Determine the empirical formula of the compound. (C = 12.0, H = 1.0, O = 16.0) b) If the mass of one mole of the compound is 242, determine its molecular formula
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A sample of fertilizer is suspected to be calcium ammonium nitrate. Describe chemical tests for each of the following ions in the sample:
a) Calcium ions; b) Ammonium ions.
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(a)Add a few drops of NaOH to an aqueous solution of the fertilizer. Forms white precipitate insoluble in excess. .
Add a few drops of aqueous sulphuric (VI) acid to another portion of aqueous solution of fertilizer. Forms a white precipitate insoluble in excess. (b)Heat the sample fertilizer in a test tube, and test gas evolved with damp red litmus paper, turn blue. Or add NaOH to the sample fertilizer and heat the mixture; test gas evolved using damp red litmus paper, turn blue.
Carbon (II) oxide is described as a “silent killer”
a) State one physical property of carbon (II) oxide that makes it a “silent killer” b) State and explain one chemical property that makes carbon (II) oxide poisonous to human beings
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(a)gas has no colour and smell.
(b)Carbon (II) oxide has high affinity for iron in the haemoglobin in the blood, or displaces oxygen from haemoglobin, the body tissues are deprived of oxygen.
Using electrons in thee outermost energy level, draw the dot (.) and cross (x) diagrams for the molecules H2O and C2H4. (H = 1, C = 6, O = 8)
i) H2O ii) C2H4 b) The formula of a complex ion is Zn(NH3)42+. Name the type of bond that is likely to exist between zinc and ammonia in the complex ion.
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Some animal and vegetable oils are used to make margarine and soap. Give the reagents and conditions necessary for converting the oils into:
a) Margarine b) Soap
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A beaker contained 75.0cm3 of aqueous copper (II) sulphate at 23.7°C. when scrap iron metal was added to the solution, the temperature rose to 29.3°C.
a) Write an ionic equation for the reaction that took place. b) Given that the mass of copper deposited was 5.83g, calculate the molar enthalpy change in kJmol-1. (specific heat capacity of solution = 4.2Jg-1 K-1, density of solution 1.0gcm-3, Cu = 63.5)
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Hydrogen sulphide is a highly toxic and flammable gas. It is normally prepared in a fume chamber
.a) Name two reagents that can be used to prepare hydrogen sulphide in the laboratory. b) One of the uses of hydrogen sulphide is to produce sulphur as shown in the following equation; 2H2S(g) + SO2(g) → 3S(s) + 2H2O(l) Identify the reducing agent in this reaction and give a reason for your answer. c) Other than production of sulphuric(IV) acid, state one commercial use of sulphur.
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(a) Iron (II) Sulphide
Hydrochloric acid (b)Reducing agent, hydrogen sulphide The sulphur changes from -2 to zero (c) Vulcanization of rubber Manufacture of sulphur drugs
The figure below shows an energy cycle.
a) Give the name of the enthalpy change ΔH1.
b) Determine the value of ΔH3.
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a) Write a nuclear equation for the decay process of carbon -14.
b) From the graph, determine the; i) Half-life of carbon -14; ii) Percentage of carbon -14 in a sample whose age is 1950 years.
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The pressure of nitrogen gas contained in a 1dm3 cylinder at -196°C was 107 Pascals.
Calculate the: a) Volume of the gas at 25°C and 105 Pascals. b) Mass of nitrogen gas(Molar volume of gas is 24dm3, N = 14.0)
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Complete the table below by writing the product formed at the electrodes during the electrolysis of the electrolytes given in the table.
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Aluminium oxide reacts with both acids and bases.
a) Write an equation for the reaction between aluminium oxide and hydrochloric acid. b) Using the equation in (a) above, calculate the number of moles of hydrochloric acid that would react completely with 153.0g of aluminium oxide. (AL = 27.0, 0= 16.0)
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Hydrate cobalt(II) chloride exists as pink crystals and anhydrous cobalt(II) chloride is a blue powder. Describe a laboratory experiment that can be used to show that the action of heat on hydrated cobalt(II) chloride is a reversible reaction.
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December 2024
AuthorMaurice Atika is a teacher and a netprenuer. |
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