MYP 10 Chemistry 2012-13
Solutions and Titrations
Worksheet
Name: _________________________________ ( )
Class: _________ Date: _____________
_________________________________________________________________________________
Solutions
1(a) Calculate the concentration of the solution formed when 0.5 mol of glucose is dissolved in 5.0 dm3 of
water.
(b) Calculate the concentration of the solution when 4.00grams of sodium hydroxide is dissolved in
200 cm3 of water.
(c) Calculate the mass of hydrated copper(II)sulfate, CuSO4.5H2O present in 25.0 cm3 of a 0.500 moldm-3
solution.
(d) Calculate the concentration (in moldm-3) of a solution of hydrochloric acid containing 14.6 grams of
hydrogen chloride in 100 cm3 of solution.
[(a)0.1 moldm-3(b)0.50 moldm-3(c)3.12g(d)4 moldm-3]
Dilution of Acids
2. Calculate the volume to which 25.0 cm3 of 5.0 moldm-3 hydrochloric acid must be diluted to produce a
concentration of 1.5 moldm-3.
Acid-base Titrations
3. Sodium hydroxide reacts with hydrochloric acid. Calculate the volume of 0.0500 moldm-3 sodium
hydroxide solution to react exactly with 25 cm3 of 0.20 moldm-3 hydrochloric acid.
[100cm3]
4. 0.558 grams of monobasic aromatic carboxylic acid, HX, was dissolved in distilled water. A few drops of
phenolphthalein indicator was added and the mixture was titrated with 0.100 moldm-3 sodium hydroxide
solution. It took 41.0 cm3 of the alkali to obtain the end-point (with a permanent pink colour). Calculate
the molar mass of the organic acid.
[136gmol-1]
5. 17.5 cm3 of 0.150 moldm-3 potassium hydroxide solution react with 20.0 cm3 of phosphoric acid, H3PO4
of concentration 0.0656 moldm-3. Deduce the equation for the reaction.
6. In a titration, 25.0 cm3 of barium hydroxide solution reacted with 20.0 cm3 of 0.100 mol/dm3 hydrochloric
acid.
(a) Write a balanced equation with state symbols for the above reaction.
(b) Calculate the concentration of barium hydroxide in mol/dm3 and in g/dm3
7. A 50.0 cm3 sample of concentrated sulfuric acid was dilaued to 1.00 dm3. A sample of the diluted sulfuric
acid was analysed by titrating with aqueous sodium hydroxide. In the titration, 25.00 cm3 of
1.00 moldm-3 aqueous sodium hydroxide required 20.0 cm3 of the diluted sulfuric acid for neutralisation.
Determine the concentration of the original concentrated sulfuric acid solution.
[12.5 moldm-3]
8. 40 cm3 of a HCl solution was diluted with water and made up to a 250 cm3 solution. 25.0 cm3 of this
diluted solution required 20.90 cm3 of a 0.01 moldm-3 NaOH solution for complete neutralisation.
What is the concentration of the original HCl solution?
[0.0523 moldm-3]
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9. A solution of sodium hydroxide contains 1.80g of hydroxide ions per dm3. 20.0cm3 of the solution reacts
with 25.00 cm3 of 0.0400 dm3 phosphoric acid (H3PO4).
(a) How many moles of sodium hydroxide react with 1 mole of phosphoric acid?
(b) What will be the chemical equation for the reaction?
[2]
*10. What mass of barium chloride must be dissolved in 25.0 cm3 solution of 0.150 mol dm-3 potassium
chloride to increase the concentration of chloride ions to 0.310 mol dm-3.
Back Titration
11. A student was asked to determine the concentration of ammonia, a volatile substance, in a commercially
available cloudy ammonia solution used for cleaning.
First the student pipetted 25.00mL of the cloudy ammonia solution into a 250.0mL conical flask.
50.00mL of 0.100M HCl(aq) was immediately added to the conical flask which reacted with the ammonia
in solution.
The excess (unreacted) HCl was then titrated with 0.050M Na2CO3(aq).
21.50mL of Na2CO3(aq) was required.
Calculate the concentration of the ammonia in the cloudy ammonia solution.
[0.114M]
12. A student was asked to determine the mass, in grams, of calcium carbonate present in a 0.125g sample of
chalk.
The student placed the chalk sample in a 250mL conical flask and added 50.00mL 0.200M HCl using a
pipette.
The excess HCl was then titrated with 0.250M NaOH.
The average NaOH titre was 32.12mL
Calculate the mass of calcium carbonate, in grams, present in the chalk sample.
[0.099g]
13. Magnesium oxide is not very soluble in water, and is difficult to titrate directly. Its purity can be
determined by use of a 'back titration' method. 4.06 g of impure magnesium oxide was completely
dissolved in 100 cm3 of hydrochloric acid, of concentration 2.0 mol dm-3 (in excess). The excess acid
required 19.7 cm3 of sodium hydroxide (0.20 mol dm-3) for neutralisation. This second titration is called
a 'back-titration', and is used to determine the unreacted acid.
(a) write equations for the two neutralisation reactions.
(b) calculate the moles of hydrochloric acid added to the magnesium oxide.
(c) calculate the moles of excess hydrochloric acid titrated.
(d) calculate the moles of hydrochloric acid reacting with the magnesium oxide.
(e) calculate the mass of magnesium oxide that reacted with the initial hydrochloric acid, hence the
% purity of the magnesium oxide.
(f) what compounds could be present in the magnesium oxide that could lead to a false value of its purity?
Explain your answer.
Redox Titration
14. Hydrated sodium carbonate has the formula Na2CO3.nH2O. An experiment was performed to determine
n, the amount of water of crystallisation. A sample of 50.00g of hydrated sodium carbonate was
dissolved in 250 cm3 of water. 20.00 cm3 of this solution reacted completely with 13.95 cm3 of
2.00 mol dm-3 hydrochlorc acid.
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Na2CO3(aq) + 2HCl(aq)  2NaCl(aq) + CO2(g) + H2O(l)
(a)
(b)
(c)
(d)
(e)
Calcuate the amount of hydrochlorc acid reacted.
Calculate the amount of sodium carbonate in the 20 cm3 of the solution used in the reaction.
Calculate the concentration of sodium carbonate in the sample.
Calculate the molar mass of the hydrated sodium carbonate.
Calculate the value of n.
[(a)0.0279ml(b)0.01395mol(c)0.6975mol/dm3(d)286.75g/mol(e)10]
15. Hydrated iron(II)sulfate has the formula FeSO4.xH2O. An experiment was performed to determine x, the
amount of water of crystallisation in hydrated iron(II)sulfate. 50.6grams of hydrated iron(II)sulfate were
dissolved in distilled water to make 250.0 cm3 of solution. 20.0 cm3 of this solution reacted completely
with 24.0 dm3 of 0.100 moldm-3 potassium dichromate(VI) solution. Use this data to determine the value
of x and hence the formula of hydraed iron(II)sulfate.
[FeSO4.7H2O]
16. 5.125g of hydrated sodium carbonate, Na2CO3.xH2O was dissolved in water and made into a 250 cm3
solution. 25.0 cm3 of this solution was placed in a conical flask. It required 35.80 cm3 of 0.050 mol dm-3
dilute sulphuric acid H2SO4 for complete reaction. Determine the value of x.
Precipitation Titrations
17. 0.010mol of an ionic chloride was dissolved in water and found to react completely with 20 cm3 of 1.00
moldm-3 silver nitrate solution. Determine the formula, using M to represent the metal.
[MCl2]
18. 14.48g of metal sulfate with the formula M2SO4 were dissolved in water. Excess barium nitrate solution
was added in order to precipitate all the sulfate ions in the form of barium sulfate. 9.336g of precipitate
was obtained.
(a)
(b)
(c)
(d)
Calculate the amount of barium sulfate BaSO4 precipitated.
Calculated the amount of sulfate ions present in the 14.48g of M2SO4.
What is the relative molecular mass of M2SO4?
Calculate the relative atomic mass of M and hence identify the meta.
[(a) 4.00 x 10-2 moles (b) 4.00 x 10-2 moles (c) 362 (d) Ar=133, Cs ]
19(a) Aqueous XO43- ions form a precipitate with aqueous silver ions. Write a balance equation for the
reaction, including state symbols.
(b) When 41.18 cm3 of a solution of aqueous silver ions with a concentration of 0.2040 mol dm-3 is
added to a solution of ions, 1.172g of the precipitates is formed.
(i) Calculate the amount (in moles) of Ag+ ions used in the reaction.
(ii) Calculate the amount (in moles) of the precipitate formed.
(iii) Calculate the molar mass of the precipitate.
(iv) Determine the relative atomic mass of X and identify the element.
[HL paper 2, Nov 03]
[(b)(i)8.401x10-3(ii)2.800x10-3(iii)418.6g/mol(iv)30.99,P]
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