WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709

Chemistry WAEC Past Questions

Clear Selections
Change Subject Post a Question Check Syllabus Study My Bookmarks Past Questions Videos Watch Video Lessons Download App

Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
41

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
42

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
43

(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
Download WAEC May/June App - Get all past questions and answers, 100% offline - 43208
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
44

Credit will be given for strict adherence to the instructions, for observations precisely recorded and accurate inferences. All tests, observations and inferences must be clearly entered in your als book, in ink, at the time they are made.

C is a mixture of an inorganic and organic compounds. Carry out the following exercises on C: Record your.observations and identity any gases evolved. State the conclusion you draw from the result of each test.

(a) Put all of C into a beaker and add 10 cm\(^3\) of distilled water: Stir the mixture thoroughly and filter. Keep both the filtrate and residue.

(b)(i) Test the filtrate with litmus paper.

(ii) To about 2 cm\(^3\) of the filtrate, add BaCI\(_{2(aq)}\) followed by dilute HCI:

(iii) To another 2 cm\(^3\) portion of the filtrate add NaOH and heat.

(c) Transfer the residue into a boiling tube and add few drops of iodine solution

View Answer & Discuss WAEC 2006
45

Burette reading (initial and final) must be given to two decimal places. Volume of pipette used must be recorded but no account of experimental procedure is required. All calculations must be done in you answer book.

A is a solution containing 6.3 g dm\(^{-3}\) of HNO\(_3\), B is a solution Na\(_2\)CO\(_3\)

(a) Put A Into the burette and titrate it against 20.0 cm\(^3\) portions of B using methyl orange indicator. Record the volume of your pipette. Repeat the titration to obtain consistent titres. Tabulate your burette readings and calculate the average volume of A used. The equation for the reaction involved in the titration is:

2HNO\(_{3(aq)}\) + Na\(_2\)CO\(_{3(aq)}\) \(\to\) 2NaNO\(_{3(aq)}\) + CO\(_{2(g)}\) + H\(_{2}\)O\(_{(l)}\)

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

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

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

(iii) mass of sodium ions in 1:0 dm\(^{-3}\) of B

[H = 1; C = 1; O = 16; N = 14; Na = 23]

View Answer & Discuss WAEC 2006
Start a Free Practice Test
 
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
Download WAEC May/June App - Get all past questions and answers, 100% offline - 43208
WAEC offline past questions - with all answers and explanations in one app - Download for free