The mole

1. In an experiment magnesium ribbon was heated in air. The product formed was found to be
heavier than the original ribbon. Potassium manganate (VII) was on the other hand, heated in
air and product formed was found to be lighter. Explain the differences on the observation made
2. In a filtration experiment 25cm3 of a solution of Sodium Hydroxide containing 8g per
litre was required for complete neutralization of 0.245g of a dibasic acid. Calculate
the relative molecular mass of the acid (Na = 23.0, O = 16, H= 1)
3. D grams of Potassium hydroxide were dissolved is distilled water to make 100cm3 of solution.
50cm3 of the solution required 50cm3 of 2.0M nitric acid for complete neutralization.
Calculate the mass D of Potassium hydroxide (RFM of KOH = 56)
KOH(aq) + HNO3(aq)------------> KNO3(aq) + H2O(l)
4. When excess dilute hydrochloric acid was added to sodium sulphite, 960cm3 of sulphuric
(IV) Oxide gas was produced. Calculate the mass of sodium sulphate that was used.
(Molar gas volume = 24000cm3 and Molar mass of sulphite = 126g)
5. The equation of the formation of iron (III) chloride is
2Fe(s) + 3Cl2(g)--------------> 2FeCl3
Calculate the volume of chlorine which will react with iron to form 0.5g of Iron (III) chloride.
(Fe = 56 Cl=35.5). Molar gas volume at 298K = 24dm3)
6. 15.0cm3 of ethanoic acid (CH3COOH) was dissolved in water to make 500cm3 of solution.
Calculate the concentration of the solution in moles per litre
[C=12, H = 1, O = 16, density of ethanoic acid is 1.05g/cm3]
7. When 1.675g of hydrated sodium carbonate was reacted with excess hydrochloric acid,
the volume carbon (IV) oxide gas obtained at room temperature and pressure was 150cm3.
Calculate the number of moles of water of crystallization in one mole of hydrated sodium
carbonate:- (Na=23, H =1, C=12, O=16, MGV at R.T.P = 24000cm3)
8. How many chloride ions are present in 1.7g of magnesium chloride crystals?
(Avogadro’s constant = 6.0 x 1023, Mg = 24, Cl = 35.5)
9. 0.84g of aluminium reacted completely with chlorine gas. Calculate the volume of chlorine
gas used (Molar gas volume is 24dm3, Al = 27)
10. 6.4g of a mixture of sodium carbonate and sodium chloride was dissolved in water to make
50cm3 solution. 25cm3 of the solution was neutralized by 40cm3 of 0.1M HCl(aq). What is
he percentage of sodium chloride in the solid mixture?
11 An unknown mass, x, of anhydrous potassium carbonate was dissolved in water and the
solution made up to 200cm3. 25cm3 of this solution required 18cm3 of 0.22M nitric (V) acid for
complete neutralization. Determine the value of x. (K=39.0, C =12.0, O =16.0)
12. Calculate the volume of oxygen gas used during the burning of magnesium (O = 16, molar
gas volume = 24,000cm3 at room temperature)
13. A hydrated salt has the following composition by mass. Iron 20.2 %, oxygen 23.0%,
sulphur 11.5%, water 45.3%
i) Determine the formula of the hydrated salt (Fe=56, S=32, O=16, H=11)
ii) 6.95g of the hydrated salt in c(i) above were dissolved in distilled water and the total
volume made to 250cm3 of solution. Calculate the concentration of the resulting salt solution
in moles per litre. (Given that the molecula mass of the salt is 278)
14. (i) Lead (II) ions react with iodide ions according to the equation;

300cm3 of a 0.1m solution of iodide ions was added to a solution containing excess lead II ions.
Calculate the mass in grams of lead II iodide formed
(ii) Identify the colour of the product formed in (d) (i)
15. a) The diagram below represents part of the structure of sodium chloride crystal

The position of one of the sodium ions in the crystal is shown as;
i) On the diagram, mark the positions of the other three sodium ions
ii) The melting and boiling points of sodium chloride are 801C and 1413C respectively. Explain
why sodium chloride does not conduct electricity at 25C, but does not at temperatures
between 801C and 1413C
b) Give a reason why ammonia gas is highly soluble in water
c) The structure of ammonium ion is shown below;

Name the type of bond represented in the diagram by N H
d) Carbon exists in different crystalline forms. Some of these forms were recently discovered
in soot and are called fullerenes
i) What name is given to different crystalline forms of the same element
ii) Fullerenes dissolve in methylbenzene while the other forms of carbon do not. Given that soot is
a mixture of fullerenes and other solid forms of carbon, describe how crystals of fullerenes can
be obtained from soot
iii) The relative molecular mass of one of the fullerenes is 720. What is the molecular mass of
this fullerene
16. Calculate the volume of oxygen gas used during the burning of magnesium (O = 16, molar
gas volume = 24,000cm3 at room temperature)
17. Study the information in the table below and answer the questions that follow

i) Write the general formula of the hydrocarbons in the table
ii) Predict the relative atomic mass of the hydrocarbons with 5 carbon atoms
iii) Determine the relative atomic mass of the hydrocarbon in (ii) above and draw its
structural formula (H=1.0, C=12.0)
18. A hydrated salt has the following composition by mass. Iron 20.2 %, oxygen 23.0%,
sulphur 11.5%, water 45.3%
i) Determine the formula of the hydrated salt (Fe=56, S=32, O=16, H=11) (3 mks)
ii) 6.95g of the hydrated salt in c(i) above were dissolved in distilled water and the total
volume made to 250cm3 of solution. Calculate the concentration of the resulting salt solution
in moles per litre. (Given that the molecula mass of the salt is 278)
19. a) Galvanized iron sheets are made by dipping the sheets in molten Zinc.
i) Explain how zinc protects iron from rusting
ii) Name the process applied in galvanization of iron with zinc
20. Calculate the percentage of copper in 1.0g of the alloy
(Cu = 63.5 Mg = 24)
21. A factory uses nitric acid and ammonia gas as the only reactant for the preparation of the
fertilizer if the daily production of the fertilizer is 4800kg. Calculate the mass of ammonia
gas used daily
(N = 14.0, O= 16.0, H = 1.0)
22. Calculate the volume of sulphur (VI) oxide gas that would be required to produce 178kg of
oleum in step 3 molar gas volume at s.t.p = 22.4 litres H = 1 O = 16 S = 32
23. Using the answer in d (ii) above, determine:
i) The volume of 1M nitric acid that would react completely with one mole of copper
(Cu = 63.5)
ii) The volume of Nitrogen (IV) oxide gas produced when one mole of copper reacts
with excess 1M nitric acid at room temperature
24. A sample of biogas contains 35.2% by mass of methane. A biogas cylinder contains 5.0kg
of the gas. Calculate:
(i) Number of moles of methane in the cylinder (Molar mass of methane = 16)
(ii) Total volume of carbon (IV) oxide produced by the combustion of methane in the cylinder
(Molar gas volume = 24.0dm3 at room temperature and pressure)
25. 0.84g of aluminium were reacted completely with chlorine gas. Calculate the volume
of chlorine gas used. (Molar gas volume is 24dm3, Al = 27)
26. 3.52g of Carbon (IV) Oxide and 1.40g of water are produced when a mass of a hydrocarbon
is completely burnt in oxygen. Determine the empirical formula of the hydrocarbon;
(H = 1 , C= 12, O = 16)
27. Calculate the number of water molecules when 34.8g Na2CO3 xH2O is heated and 15.9g of
anhydrous Na2CO3 obtained (H=1, O=16, Na= 23, C = 12)
28. A weighed sample of crystallined sodium carbonate (Na2CO3nH2O) was heated in a crucible
until there was no further change in mass. The mass of the sample reduced by 14.5%. Calculate
the number of moles (n) of water of crystallization (Na = 23, O = 16, C = 12, H = 1)
29. In a reaction 20cm3 of 0.1 M Sodium Carbonate completely reacted with 13cm3 of dilute sulphuric acid. Find the molarity of the sulphuric acid used.
30. An organic compound P contains 68.9% carbon, 13.5% hydrogen and 21.6% oxygen.
The relative formula mass of p is 74. Determine its molecular formula. [C=12, H=1, 0=16]
31. Campers GAZ cylinder contains about 1.12dm3 of butane measured at 0o and 1atm. Given that
25% of heat is lost, what is the maximum volume of water at room temperature which can be
boiled to 100oC in order to make some coffee?

(Specific heat capacity of water = 4.2J g-1C-0c, density of water 1gcm-3 Molar gas volume 22.41 at s.t.p)
32. An aqueous solution containing anhydrous sodium carbonate was prepared by dissolving
19.6g of the salt in 250cm3 of distilled. Calculate the volume of 2M of magnesium chloride
solution required to precipitate all the carbonate ions in the solution.
(Na=23, C= 12; O = 16; Mg = 24; Cl =35.5)
33. 10.08g of ethanedioic acid (H2C2O4.xH2O) crystals were dissolved in water and made to
1dm3 solution. 25.0cm3 of this solution was completely neutralized by 20cm3 of 0.2M
sodium hydroxide solution.
Calculate
i) Molarity of the acid
ii)the value of x in H2C2O4xH2O acid
34. 1.6g of magnesium metal is reacted with excess hydrochloric acid. Calculate the volume
of hydrogen gas produced
(Molar gas volume at stp = 22.4dm3 Mg=24)
35. 60 litres of sulphur(IV) oxide were made to react with 40 litres of oxygen.
a) Which reactant was in excess and by how much?
b) What is the volume of the product?
36. During welding of cracked railway lines by thermite 12.0g of oxide of iron is reduced by
aluminium to 8.40g of iron. Determine the empirical formula of the oxide
(Fe= 56.0, O= 16.0)