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3961

Burette readings(initial and final) must be given to two decimal places. Volume of pipette user must also be recorded but on account of experimental procedure is required. All calculations must be done in your answer book. A is O.050 mol dm\(^{-3}\) of acid HX. Bis a solution of NaOH containing 0.025 moles per 250 solutions.

(a) Put A into the burette and titrate it against 20.00 cm\(^3\) or 25.00 cm\(^3\) portions B using phenolphthalein as indicator. Tabulate your readings and calculate the average volume or A used.

 

(b) your results and the information provided above, calculate the;

(i) amount of acid in the average

(ii) amount of base in 20.00 cm\(^3\) or 25.00 cm\(^3\);

(iii) mole ratio of acid to base

 

(c) Write a balanced chemical equation for the reaction between the acid H\(_y\)X and the base NaOH

(d) State the basicity of the acid H\(_y\)X. 

View Answer & Discuss WAEC 2008
3962

(a) State an indicator suitable for the titration of;

(i) dilute HCl and NaOH\(_{3(aq)}\)

(ii) dilute CH\(_3\)COOH and KOH\(_{(aq)}\)

(iii) dilute HCl and NH\(_{3(aq)}\).

Give a reason for your answer in each case.

(b) Calculate the volume of water that would be added to 50 cm\(^3\) of 0.10 mol dm\(^{-3}\) of HCI to dilute it to 0.010 mol dm \(^{-3}\)

(c) Name one gas that could be used to demonstrate the fountain experiment.

View Answer & Discuss WAEC 2007
3963

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.

C is a mixture of two inorganic salts. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.

(a) Put all of C in a test tube and add about 10 cm\(^3\) of distilled water. Stir, filter, and keep the filtrate and the residue.

(b) Put the residue into a test tube and add about 5 cm\(^3\) of dilute HCl. Shake to dissolve 

(i) To about 2 cm\(^3\) of the solution, add NaOH\(_{(aq)}\) in drops and then in excess

(ii) To another 2 cm\(^3\) portion of the solution, add NH\(_{3(aq)}\) in drops and then in excess.

(c) To about 2 cm\(^3\) portion of the filtrate, add few drops of dilute HNO\(_3\), and then AgNO\(_{3(aq)}\) a followed by aqueous NH\(_3\) in excess.

View Answer & Discuss WAEC 2007
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3964

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. 

A is a solution containing 1.04 g HCl per 500 cm\(^3\) of solution. B was prepared by diluting 50.0 cm\(^3\) of a saturated solution of Na\(2\)CO\(_3\) at room temperature to 1000 cm\(^3\)

(a) Put A into the burette and titrate it against 20.0 cm\(^3\) or 25.0 cm\(^{3}\) portions of B using methyl orange as indicator. Repeat the titration to obtain consistent titres. Tabulate your results and calculate the average volume of acid used. 

9b) From your results and information provided above, calculate the; 

(i) concentration of A in moldm\(^{-3}\)

(ii) concentration of B in mol dm\(^{-3}\)

(iii) solubility of Na\(_2\)CO\(_3\) in mol dm\(^{-3}\) 

(iv) volume of CO\(_2\) that would be liberated from 1 dm\(^3\) of B if the titration were carried out at s.t.p. 

The equation for the reaction is Na\(_2\)CO\(_{3(aq)}\) + 2HCl\(_{(aq)}\) \(\to\) 2NaCl\(_{(aq)}\) + H\(_2\)O\(_{(l)}\) + CO\(_{2(g)}\) 

[H = 1; C = 12; O = 16; Na = 23; Cl = 35.5; Molar volume of gas at s.t.p = 22.4 dm\(^3\)]

View Answer & Discuss WAEC 2007
3965

(a) Consider the following compounds: MnO\(_2\), NaHCO\(_3\), Na\(_2\)CO\(_3\), NH\(_4\)CI cnd Pb(NO\(_3\))\(_2\) Select the compound(s) which;

(i) has a black colour

(ii) is a basic oxide:

(ii) sublime on heating

(iv) dissolves in water to give a solution of pH less than 7.

 

(b) State the colour of each af the following aqueous Solutions:

(i) Calcium hydroxide;

(ii) iron (III) trioxonitrate (V):

(ii) Copper (II) tetraoxosulphate (VI);

(iv) Poassium heptaoxodichromate (VI).

 

(c) Give one example of a neutral oxide which is a colourless liquid at room temperature.

(d) Draw and label a diagram for a set-up that can be used for the separation of two immiscible liquids

View Answer & Discuss WAEC 2006
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