Question Library

Liquefied air is mainly a mixture of nitrogen and oxygen which can be separated into its components by fractional distillation (Boiling point of nitrogen is 196^\circC, Boiling point of oxygen is 174^\circC) (a) Name the fraction which distills over first. Give the reason for your answer. (b) Give another industrial application of fractional distillation as a separation technique.

(a)(i) List two physical properties used as criteria for purity of substances (ii) describe how you would prepare a pure, dry sample of sodium chloride crystals by a neutralization reaction, using bench reagents. (iii) Give two other general methods for preparing soluble salts. (b) Explain the following observations: (i) a sheet of iron placed in dilute copper (II) tetraoxosulphate (VI) solution reddish brown; (ii) the white gelatinous precipitate formed when a few drops of sodium hydroxide solution are added to a solution of aluminium salt dissolves in excess alkali; (iii) the pale green prepared iron(II) chloride solution changes to brown on bubbling chlorine gas through it. (iv) Write a balanced equation for the reaction of dilute hydrochloric acid with marble. List two industrial process in which limestone is used as a raw material.

Consider the reaction represented by the equation: 2SO\(_{2(g)}\) + O\(_{2(g)}\) 2SO\(_{3(g)}\). \(\Delta\)H = 188KJ. (a) Write an expression for the equilibrium constant (b) Sketch an energy diagram for the forward reaction, showing the profile for the catalyzed and non-catalyzed systems. (c) state the reason, the effect of the following on the position of equilibrium of the system: (i) increase in temperature (ii) increase in pressure; (iii) removal of some of the SO\(_3\) produced; (iv) presence of V\(_2\)O\(_5\) (d)(i) Write equations to show how the sulphur(VI) oxide is converted to tetraoxosulphate(VI) acid in the contact process (ii) Give two uses of tetraoxosulphate(VI) acid.

(a)(i) Define the term addition polymerization (ii) What type of organic compounds undergo addition polymerization (iii) List two factors which affect the strength of polymers (b) The diagram below shows some reaction pathways involving ethanol (i) Write the name and structural of the organic product X (ii) State the reagent for the conversation indicated as step A. (iii) What type of reaction will ethanol undergo CH\(_3\)CH\(_2\)COOH during the process of conversation indicated as step B? (c)(i) Write three balanced equation for the complete combustion of ethanol in :date the volume of oxygen required at s.t.p for the complete combustion of ethanol. (H = 1, C = 12, O = 16, molar volume of gases at s.t.p. = 22.4 dm\(^3\)) (d)( i} State two substances produced when coal is heated in the absence of air (ii) What name is given to the process in (d)(i) above? (iii) State the importance of the non-volatile residue of the process named in (d)(iii) to the iron and steel industry.

(a)(i) Define oxidation in terms of electron transfer. (ii) Write balanced equations for the half reactions for the following changes in acidic solution: Mn0\(^-_4\) + Fe\(^{2+}\) —> Mn\(^{2+}\) + Fe\(^{3+}\) (b)(i) Distinguish between an electrolytic celI and an electrochemical cell. (ii) Sketch a cell for the electrolysis of molten magnesium chloride. Lable the anode and the cathode and indicate the direction of electron flow. Give the electrode reactions. (iii) Give one reason why a platinum anode is not suitable for the eloctrolysis in (b)(i) above. (c) Calculate the mass of lead that would be deposited from a solution of lead (II) trioxonitrate by the same quantity of electrically depositing 1.35g of copper. (Cu = 63.5, Pb = 207)

All your burette readings (initial and final) as well as the size size of your pipette, must be recorded but no account of experimental procedure is required. All calculations must be done in your answer book. Xg of pure potassium trioxocarbonate (IV) was treated with 1dm\(^3\) of 0. 25M tetraoxosulphate (VI) acid to obtain solution A which contains excess acid. B is a solution containing 2.8g of potassium hydroxIde per 250cm\(^3\) solution. (a) Put A into the burette and titrate with 20cm\(^3\) or 25cm\(^3\) portions of B. using methyl orange as indicator. Record the volume of your pipette. Tabulate your burette readings and calculate the average volume of acid used. (b) From your results and the information given. Calculate the; (i) concentration of the excess acid in A in mol dm\(^3\) (iii) value of X. The equation for the reaction between the excess acid the potassium hydroxide is H\(_2\)SO\(_4\) + 2KOH \(\to\) K\(_2\)SO\(_4\) [H = 1. C = 12, O = 16. S = 32, K = 39]

Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for accurate inferences. All tests, Observations, and inferences must be clearly entered in your answer book, in ink, at the time they are made. Carry out the following exercises on sample C. Record your observations and identify any gases evolved (a) Put all of C into a test tube and add about 5cm\(^3\) of water. Shake the mixture and filter. Keep both the residue and the filtrate (b) Divide the filtrate into two portions; (i) To the first portion, add a few drops of dilute trioxonitrate (V) acid followed by about 1cm\(^3\) of silver trioxonitrate (V) solution (ii) Add excess aqueous ammonia to the mixture in (i) above (iii) To the second portion, add about 2cm\(^3\) of dilute sodium hydroxide solution and warm gently (c) Add about 2cm\(^3\) of dilute hydrochloric acid to the residue from (a) above and warm gently. Filter if necessary and divide the resulting solutio into two portions. (i) To the first portion add dilute sodium hydroxide solution in drops until it is in excess (ii) To the second portion, add aqueus ammonia in drops until it is in excess.

(a)(i) Give one laboratory use of activated charcoal (ii) A piece of phosphorus and some magnesium ribbon were burnt in two separate jars of oxygen. Water was then added to dissolve the product. State the action of litmus on each of the resulting solutions (b) Give one chemical test to distinguish between CH\(_3\)CH\(_2\)OH and CH\(_3\)COOH. (c) Describe how you would dilute accurately a solution containing 0.10 mole of the solute per dm\(^3\) of solution to 0.010M.

From the words or groups of words lettered A to D, chose the word or group of words that best completes the sentence. You are not sure where you placed the book....?

From the words or groups of words lettered A to D, chose the word or group of words that best completes the sentence. We arrived when the hall ...arranged so we stood outside.

From the words or groups of words lettered A to D, chose the word or group of words that best completes the sentence. She doesn't know you like your food hot...?

From the words or groups of words lettered A to D, chose the word or group of words that best completes the sentence. It's certain we shall travel by train ...?

From the words or groups of words lettered A to D, chose the word or group of words that best completes the sentence. ......of what he said made no sense.

The problem of selection in the book trade involves

Read the following passage carefully and then answer the questions on it. A study conducted in Nigeria recently recognized three varieties of spoken English. Speakers of the first variety exhibit characteristics of a very long and difficult process of 'internal interpretation from the mother-tongue into English. Thinking and expression do not go closely together. A listener would notice this from the way the speaker pauses before expressing himself, apparently deciding which words to use and how to arrange them. Thus, thinking is exclusively through the medium of the mother-tongue and English is thus a poor shadow of the original thoughts of the speakers. Utterances heard invariably have to be translated silently into the mother-tongue to be maximally meaningful, and then responses are translated from the mother-tongue into English. Consequently, the long, indirect routes make statements slow, halting and jerky. The second variety speakers exhibit features described above but to a much lesser degree. internal translations from the mother-tongue to English still take place during the speaker's expression of opinions and complex concepts but the process now takes a shorter span of time. With ordinary words or simple ideas, internal interpretations need not intervene between the points at which the thought is conceived and the time it is given verbal expression. Discussions are quicker and smoother though these might not always be entirely free from minor halting gaps. With the third variety speakers, thought is almost entirely in English and translation is not needed. The speaker has a wealth of linguistic weapons to choose from to express the minute distinctions between similar concepts - and these come quickly and easily. Thus for instance, whereas speakers of the lower varieties have only the word 'rain', the speaker of variety III recognizes distinctions between 'shower', down-pour' drizzle'. 'mist'. 'deluge', etc.. and uses each in the appropriate context. Also, his mastery of the sounds and features of the English Language equips him to express the utterances accurately and automatically without having to pause and think of the correct version of a sound since he masters the various distinctions in the pronunciation of each vowel and each consonant. We need to recognize, however, that most Nigerian learners of English 'graduate' from one variety to another, from the lowest stratum of variety Ito the highest stratum of that variety. and then to variety II and so on until they achieve variety III. Length of periods of education. exposure to standard English and a personal conscious effort play major roles in deciding what variety a particular speaker uses. Finally, we must recognize that most speakers of the higher varieties are still capable of reverting to the lower ones, if they choose. Thus we can find even a Nigerian professor of phonology switching to the lowest stratum of variety I if he feels so inclined when discussing with a house-servant or a porter. (a) In three sentences. one for each, summarize the distinctive characteristics of the speakers of the three varieties of English described in the passage. (b) In two sentences, one for each, describe the conditions under which a person can: (i) move from lower varieties to the upper ones: (ii) switch from a higher variety to a lower one.