MYP 10 Chemistry 2012-13
Stoichiometry Worksheet
Name: _________________________________ ( )
Class: _________ Date: _____________
_________________________________________________________________________________
1. The element rhenium consists of 2 isotopes, 185Re and 187Re in the atomic ratio 2:3. Calculate the
relative atomic mass of rhenium.
2. Calculate the mass of :
(a) 0.75 mol of NiCl2.2H2O
(b) Al(OH)3 containing 0.02 mol of OH- ions
(c) 6.5 dm3 of neon (at r.t.p.)
(d) 6.02 x 1023 molecules of S8
[124.3g, 0.520g]
3. Calculate the number of particles in the following amounts of substance.
(a) Carbon atoms in 1.00g of table sugar, C12H22O11
(b) 0.0763 mol sodium chloride formula units, NaCl
4. Calculate the number of moles of subtsance in each of the following.
(a) 75 cm3 of carbon dioxide at rtp.
(b) 5.72g of sodium carbonate crystals, Na2CO3.10H2O
(c) ions in 4.0kg of Na2SO4
[2.11 x 1022,4.59 x 1022]
[0.00312,0.0200,84.4]
5. The female of the American cockcroach secretes a chemical (pheromone) of molecular formula
C11H18O2 to which the male of the species is attracted. It is reported that the male will respond to as
few as 60 molecules of the pheromone. What is the mass, in grams, of these 60 molecules?
[1.82 x 10-20]
6. Calculate the following:
(a) The number of moles of NaOH in 1.5 dm3 of 2.5 mol dm-3 NaOH.
(b) The concentration of Fe2+ in a solution containing 1.96g of (NH4)2Fe(SO4)2.6H2O dissolved in
0.1 dm3 of solution.
(c) The mass of Pb(NO3)2 needed to make 100 cm3 of a solution containing 0,2 mol dm-3 with
respect to nitrate ions.
[3.75,0.0500moldm-3,3.31g]
7. 10 cm3 of ethene, C2H4, is burned in 40 cm3 of oxygen, producing carbon dioxide ad some liquid
water. Some oxygen remained.
(a) Write the equation for the complete combustion of ethene.
(b) Calculate the volume of carbon dioxide and the volume of oxygen remaining.
[(b)20 cm3CO2,10 cm3O2]
8(a) Write an equation for the formation of zinc iodide from zinc and iodine.
(b) 100.0g of zinc is allowed to react with 100.0g of iodine producing zinc iodide. Calculate the
amount (in moles) of zinc and iodine, and hence determine which reactant is in excess.
(c) Calculate the mass of zinc iodide that will be produced.
[HL paper 2, May 04]
[(b)Zn:1.530mol,I2:0.3940mol(c)125.8g]
9. Calcium and hydrochlric acid react according to the equation:
Ca(s) + 2HCl(aq)  CaCl2(aq) + H2(g)
(a) 0.122g of calcium metal was added to 25.0cm3 of 1.23 mol dm-3 solution of hydrochlroic acid
and teh hydrogen gas was collected at room temperature and pressure.
(i)
Calculate whether the calcium or hydrochloric acid was in excess.
(ii)
Hence calculate the volume of hydrogen gas produced.
[HCl, 73.2cm3]
10. A balloon, which can hold a maximum of 1000 cm3 of nitrogen before bursting, contains 955 cm3 of
nitrogen at 50C.
(a) Determine whether the balloon will burst if the temperature is increased to 300C.
(b) Use the kinetic theory to explain what happens to the molecules of nitrogen inside the balloon as
the temperature is increased to 300C.
[(a)1041 cm3]
11. Bones contain a complex mixture of calcium salts, protein and other material. When a bone is
strongly heated in a current of air, the only residue is calcium oxide. From a sample of 50.0 g of
bone, 14.0g of calcium oxide were obtained. What is the percentage by mass of calcium in the bone?
12. Analysis of a 8.456g sample of a silicon-chlorine compound shows that it contains 6.519g of
chlorine. Calculate the empirical formula of the compound.
13. Ascorbic acid (vitamin C) is an organic compound containing carbon , hydrogen and oxygen. When
1.000g of ascorbic acid was completely burnt in oxygen, 1.500g of carbon dioxide and 0.405g of
water were formed. Calculate the empirical formula of ascorbic acid.
[C3H4O3]
14. 2.40g of an organic compound consisting of carbon, hydrogen and oxygen only gave, on combustion,
3.52g of carbon dioxide and 1.44g of water. The relative molecular mass of the compound was
found to be 60.0. What are the emipirical and moleculat formulae of the compound?
15. Sodium azide, NaN3, is made for use in car ‘air bags’. When this compound is heated to 3000C, it
rapidly decomposes into its elements. What volume of gas, at room temperature and pressure, would
be produced by the decomposition of one mole of sodium azide?
16. What volume of 0.0500 mol dm-3 K2Cr2O7 solution should you transfer into a 500 cm3 volumetric
flask in order to dilute the solution to 0.0200 mol dm-3?
[200cm3]
17. In a titration of HNO3, a student added a few drops of phenolphthalein indicator to 50.00 ml of acid
in a flask. He quickly added 20.00 cm3 of 0.0502 mol dm-3 aqueous NaOH but overshot the endpoint, and the solution turns deep pink. Instead of starting over, he added 30.00 cm3 of the acid, and
teh solution turns colourless. After that, it took 3.22 cm3 of the NaOH to reach the end-point. What is
teh concentration of the HNO3 solution? How many moles of NaOH were in excess after the first
titration?
[0.0146]
Volumetric Analysis
1. 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 mol dm-3 NaOH solution for complete neutralisation.
What is the concentration of the original HCl solution?
[0.0523]
2. What volumes of 0.500 mol dm-3 potassium chloride and 0.100 mol dm-3 potassium chloride must be
mixed to give 2 dm3 of 0.280 mol dm-3 potassium chlroide solution.
[0.900dm3 0.5M KCl & 1.1dm3 0.1M KCl]
3. 3.0g of impure Na2CO3.10H2O was dissolved to make 100 cm3 of solution. 10.0 cm3 was titrated
against HCl of concentration 4.38g dm-3. 16.4 cm3 of acid was needed for neutralisation.
(a) Calculate the number of moles of acid used.
(b) What is the number of moles of Na2CO3 used in the titration?
(c) Calculate the concentration of the sodium carbonate solution in mol dm-3.
(d) What is the percentage purity of the crystals?
[1.97 x 10-3, 9.84 x 10-4, 0.0984 moldm-3,93.8%]
4. 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]
5. 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.
6. A nail of mass 1.40g was dissolved in an excess of dilute sulphuric acid to form 100 cm3 of solution.
A 10.0 cm3 sample of this solution required 4.0 x 10-4 mol of manganate (VII) for complete
oxidation. Assuming that iron in the nail was converted entirely into Fe2+(aq), calculate the
percentage of iron in the nail.
7. 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.
8. Distilled water is added to 24.00 cm3 sulphuric acid to give a total volume of 250 cm3. When 25.0
cm3 of this solution is titrated, it required 22.80 cm3 of 1.325g dm-3 of NaOH. Calculate the original
concentration of sulphuric acid.
[0.157 mol dm-3]
9. 1.350g of an insoluble carbonate, MCO3, was dissolved in 250 cm3 of a 0.203 mol dm-3 hydrochloric
acid solution. The resulting solution was boiled to remove all the carbon dioxide produced. 25.0 cm3
of the solution was titrated with standard sodium hydroxide solution of concentration 0.100 mol dm-3.
The amount needed was 24.10 cm3. Deduce the identity of M.
[Ca]
10. 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.
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]
11. 0.375g of ethanedoic acid, (COOH)2.xH2O is dissolved in distilled water to make 250 cm3 of
solution. 25.0 cm3 of this ethanedoic acid solution required 30.00 cm3 of a solution containing
0.340g dm-3 of hydroxide ions for complete neutralisation.
Calculate
(a) the concentration of anydrous ethanedoic acid in 1 dm3 of the solution prepared above as mol
dm-3 and hence g dm-3.
(b) the mass of water associated with the amount of anhydrous ethanedoic acid in 1 dm3 of the
solution.
(c) the value of x in the formula.
[x = 2]
12(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]
13. A solid sample contains a mixture of sodium chloride, NaCl and ammonium chloride, NH4Cl. The
following was carried out to determine the percentage by mass of NH4Cl in the solid sample.
Step 1 : 4.30g of the above solid sample was warmed with 100 cm3 of 1.00 mol dm-3 of sodium
hydroxide solution until all the ammonia was driven off.
Step 2 : 10.0 cm3 of the above reaction mixture (contains excess sodium hydroxide) required 20.0
cm3 of 0.0625 mol dm-3 sulphuric acid for neutralisation.
(a) Write an equation to represent the reaction taking place on step 1.
(b) Calculate the amount of NaOH used to react with the solid sample in step 1.
(c) Determine the amount of NaOH unreacted in step 1 from the titrtaion result in step 2.
(d) Use the equation from (a) and the answers from (b) and (c), calculate the amount of NH4Cl in the
solid sample and hence find the percentage mass of NH4Cl in the solid sample. [93.3%]