Chemistry Past Questions And Answers
How many moles of carbon(iv)oxide contains 16.0g of oxygen? [ C = 12.0, O = 16.0 ]
- A. 0.20 mol
- B. 0.25 mol
- C. 0.40 mol
- D. 0.50 mol
(a) (i) Name the ore mostly used in the extraction of aluminium.
(ii) Name two major impurities in the ore named in (a)(i).
(iii) Name the material used in making the electrodes in the extraction of aluminium.
(iv) Givetwo reasons why aluminium is commonly recycled.
(v) Explain briefly why the anode has to be replaced at regular intervals during the extraction of aluminium.
(b) A current of 0.75 amperes was passed through an electrolysis containing chromium ions for one hour and four minutes. If the mass of chromium deposited was 0.52 g, calculate the:
(i) quantity of electricity passed;
(ii) moles of chromium deposited;
(iii) quantity of electricity required to deposit one mole of chromium;
(iv) charge on the chromium ion.
[Cr = 52.0, 1 F = 96500 C]
(c) In the contact process for the manufacture of tetraoxosulphate(VI) acid, the following reaction occurs:
2SO\(_2\)\(_{(g)}\) + O\(_2\)\(_{(g)}\) 2SO\(_3\)\(_{(g)}\) H = - 197 kJ mol\(^{-1}\)
(i) Name the catalyst used in the reaction;
(ii) State the optimum temperature for this reaction;
(iii) What would be the effect on the yield of SO\(_3\) if a temperature higher than the optimum is used?
(d)(i) State two chemical methods by which temporary hardness of water can be removed.
(ii) Write a balanced chemical equation for each of the methods stated in (d)(i).
View Discussion (0)WAEC 2018 THEORYThe gas that will form a white precipitate with acidified silver trioxonitrate (v) is
- A. NH3 B. SO2
- C. CO2
- D. HCL
- D. HCL
On exposing palm wine to air for some days, it becomes sour owing to the conversion of
- A. glucose to ethanol
- B. glucose to gluconic acid
- C. ethanol to ethanoic acid
- D. ethanol to ethanal
The colour changes observed when testing for reducing agents using acidified potassium heptaoxodichromate (IV) solution is
- A. yellow to purple
- B. orange to green
- C. green to orange
- D. purple to yellow
Arrange the following compounds in decreasing order of their boiling points: \(NH_3\), HF, \(SiH_4\), \(CH_4\)
- A. HF,\(NH_3\), \(SiH_4\), \(CH_4\)
- B. \(CH_4\), \(SiH_4\), HF, \(NH_3\),
- C. \(NH_3\),\(CH_4\), \(SiH_4\), HF
- D. \(CH_4\), \(SiH_4\), \(NH_3\), HF
A 0.1moldm-3 solution of sodium hydroxide was diluted with distilled water to 0.001moldm-3. What is the dilution factor?
- A. 1000.00
- B. 100.00
- C. 10.00
- D. 0.01
One of these reactions represents the laboratory preparation of hydrogen.
- A)C(s) + H\(_2\)O(l)\(\rightarrow\) CO(g) + H\(_2\)(g)
- B)2Na(s) + 2H\(_2\)0(1) \(\rightarrow\) 2NaOH(aq) + H\(_2\)(g)
- C)Cu(s) + H\(_2\)O(l) \(\rightarrow\) CuO(s) + H\(_2\)(g)
- D)Zn(s) + 2HCl(aq) \(\rightarrow\) ZnCl\(_2\)(aq) + H\(_2\)(g)
(a) Name the crystalline allotrope of sulphur that is stable at room temperature.
(b)(i) Give one example of a fuel that contains significant amount of sulphur as an impurity.
(ii) State one environmental disadvantage of using a fuel that has high sulphur content
View Discussion (0)WAEC 1992 THEORY(a) (i) Define a base according to Arrhenius concept.
(ii) Give one example of an Arrhenius base.
(iii) Identify each of the following substances in aqueous solutions as strong electrolyte, non-electrolyte or weak electrolyte.
I. C\(_{12}\)H\(_{22}\)O\(_{11}\) II. NH\(_3\) Ill. NaOH
(iv) Write a balanced equation to represent the reaction between CH\(_3\)COOH and KOH.
(b) Calculate the volume of 0.500 mol dm\(^{-3}\) HCI required to neutralize 20.00 cm\(^3\) of 0.300 mol dm\(^{-3}\) NaOH.
(c) Give the IUPAC name of each of the following salts: (ii) NaOCI; (iii) Mg(HCO\(_3\))\(_2\).
(d)(i) Define the term standard solution.
(ii) Consider the following compounds: NaOH and Na\(_2\)CO\(_3\). Which of the compounds is suitable for the preparation of a standard alkaline solution? Give reason for your answer
(iii) Fe completely reacted with dilute HCI.
I. Write an equation for the reaction
II. If 3.08g of Fe completely reacted with 50.0 cm\(^3\) of 2.20 mol dm\(^{-3}\) HCI, calculate the relative atomic mass of the metal.
View Discussion (0)WAEC 2010 THEORY