Waec 2013 Chemistry Past Questions And Answers
A substance is said to be impure if
- A. its melting point range is wide
- B. it dissolves in water with difficult
- C. it has a low melting point
- D. it is coloured
(a)(i) What is the common name given to the group VII elements?
(ii) Name the hydrides of the first two elements in group VII.
(iii) State three chemical properties of group VII elements.
(b) Copy and complete the following table:
| Particles | Number of Neutrons | Number of electrons | Number of prontons | Mass Number |
| W\(^{2+}\) | 12 | 24 | ||
| X\(^{2+}\) | 8 | 16 | ||
| Y | 13 | 27 | ||
| Z | 12 | 11 |
(c)(i) Define each of the followinc processes: I. nuclear fission; II. nuclear fusion.
(ii) Give one use of each process in (c)(i).
(d)(i) List three types of radiation that are produced during radioactivity.
(ii) Arrange the radiations listed in
(d)(i) in order of increasing: I. penetrating power; II. ionizing power.
View Discussion (0)WAEC 2013 THEORYThe following factors affect the solubility of a solid in a given solvent except
- A. nature of solute
- B. nature of solvent
- C. pressure
- D. temperature
Which of the following materials is classified as a non-biodegradable pollutant?
- A. Animal hide
- B. Paper
- C. Plastic
- D. Wood
Which of the following arrangements represents the correct order of electronic energy level?
- A. 1s 2p 2s 3p 3s 3d 4s
- B. 1s 2s 2p 3s 3p 3d 4s
- C. 1s 2s 2p 3s 3p 4s 3d
- D. 1s 2s 3s 2p 3p 4s 3d
Which of the following cells produce electrical energy from chemical reactions? l. Lead-acid battery ll. Dry cell III. Deniell cell IV Electrolytic cell
- A. l and ll only
- B. l, ll, and III only
- C. lll and IV only
- D. I and III only
The molecule which has a linear shape is
- A. CH4
- B. NH3
- C. H2S
- D. CO2
Which of the following organic compounds would decolourize bromie water?
- A. Benzene
- B. Cyclobutane
- C. Hexane
- D. Pentane
Which of the following variables is a measure of the average kinetic energy of the molecule of a gas?
- A. Density
- B. Pressure
- C. Temperature
- D. Volume
(a)(i) Define each of the following terms: I. normal salt. II. acid salt.
(ii) Tetraoxosulphate (VI) acid and sodium hydroxide react to produce salt and water. Write a balanced chemical equation fir the formation of: I. a normal salt; II. an acid salt.
(b)(i) Explain briefly the term acid-base indicator.
(ii) Copy and complete the following table.
Indicator | , Colour in acidic medium | , Colour in basic medium |
Methyl orange | ||
Phenolphthalein |
(iii) For each of the following titrations, state the most suitable indicator: I. strong acid against strong base; II. strong acid against weak base; iii. weak acid against strong base.
(c) Baking soda and hydrochloric acid react according to the following equation:
NaHCO\(_{3(aq)}\) + HCI\(_{(aq)}\) ---> NaCl\(_{(aq)}\) CO\(_{2(g)}\) + H\(_2\)O\(_{(l)}\). Calculate the mass of baking soda that would produce 10g of ccrbon (IV) oxide. [H = 1.00, C = 12.0, 0 = 16.0, Na = 23.0]
(d) Give a reason why a given mass of sodium hydroxide pellets cannot be used to prepare a standard solution.
NaHCO\(_3\) + HCI --> NaCI + CO\(_2\) + H\(_2\)O
84g NaHCO\(_3\) --> 44g CO\(_2\)
Xg --> 10g CO\(_2\)
Xg = \(\frac{84 \times 10}{44}\)
= 19.09g
= 19.1g.
(d) give a reason why a given mass of sodium hydroxide pellets cannot be used to prepare a standard solution: Sodium hydroxide absorbs water/deliquescent and absorbs carbon IV oxide from air/and this would make mass taken unreliable/add to its mass.
View Discussion (0)WAEC 2013 THEORY