CHEMISTR WORKSHEET 1
(1)Define the following terms:(a) atom (b) element © compound (d)ion
(e)Molecule(F)Mole(G)Relative atomic mass (h)Relative molecular mass (I)Molecular(J)molar
volume(K)mass number (l)concentration (m)dilution (n)Molarity
(2)What is the difference between the following terms (a)Molar mass and relative atomic
mass(b)Relative Molecular mass and relative formula mass(C)Theoretical and actual yield(D)Empirical
formula and molecular formula
(3)Work out the Mr for each of these, and say whether it is the relative molecular mass or the
relative formula mass:
(b)oxygen, O2 (b) iodine, I2 (c) methane, CH4 (d) chlorine, Cl2 ( e)butane, C4H10 (f ) ethanol, C2H5OH
(g ) ammonium sulfate (NH4)2SO4 (h)magnesium nitrate Mg(NO3)2
(4)64 g of copper reacts with 16 g of oxygen to give the black compound copper(II) oxide.Using the
law of conservation of mass and law of definite proportion in chemical combination;
(a).What mass of copper will react with 32 g of oxygen?
(b).What mass of oxygen will react with 32 g of copper?
(c).What mass of copper(II) oxide will be formed, in b?
(d).How much copper and oxygen will give 8 g of copper(II) oxide?
(5)Calculate the percentage of (a)Fe in its ores magnetic(Fe3O4) and hematite (Fe2O3 ) and how much
of Fe can be recovered from 25.00g of each ore(b)Mg in Mg(NO3)2
(6)How many gram of oxygen can be produced from decomposition of 100.g of KCIO3?
(7)Iron reacts with excess sulfuric acid to give iron(II) sulfate. The equation for the reaction is:
Fe(s) + H2SO4(aq) ----------->- FeSO4(aq) + H2(g)
5g of iron gives 13.6 g of iron(II) sulfate.
(a )Using excess acid, how much iron(II) sulfate
can be obtained from:(i)10 g of iron? (ii) 1 g of iron?
(b)How much iron will be needed to make 136 g of iron(II) sulfate?
(c)A 10 g sample of impure iron(II) sulfate contains 8 g of iron(II) sulfate. Calculate the percentage
purity of the iron(II) sulfate.
(8)The avogadro’s number can be used to convert the number of atoms molecules and ion to moles.
(a)How many moles of silver are equal to 2.57 X 1011? (b)How many moles of H2SO4 do you have if you
there are 1.64 x 1012 molecules of H2SO4? (c)2.845 x 1012 potassium ions equals how many moles of
potassium ions?(D)If there are 8.24 x 1022 molecules of NaCl in a salt shaker, what is the mass of the
Salt?(e)how many molecules of water equal to 0.0524 moles of H2O ?
(10)Calculate the molar mass of each of the following compounds: (a) AgCl (b) CaBr2 (c)Li2O
(d)C6H12O6
(e)Fe(NO3)3 (f)Al2(SO4)3
(11) Using the conversion factor [ Molar Mass = 1 Mole] and the formula, solve the following
problems using dimensional analysis. Keep track of your units!
a) Calculate the mass of5.634 moles of HCN.
b) Calculate the moles of 257.354g of K2CrO4
c) Calculate the mass of 0.467 moles of CaBr2
d) Calculate the moles of 12.354 grams of C6H12O6
e) Calculate the mass of 8.26 moles of KClO4
f) Calculate the moles of 35.7 milligrams of Sr(NO3)2
(12)The reaction between magnesium and oxygen is:
2Mg(s) +O2(g)----------> 2MgO (s)
(a)How many moles of magnesium atoms react with 1 mole of oxygen molecules?
(b)How many grams of oxygen react with:
(i) 48 g of magnesium? (ii) 12 g of magnesium?
(13) Copper(II) carbonate breaks down on heating, like this:
CuCO3(s)--------> CuO (s) + CO2(g)
(a)Find the mass of 1 mole of each substance taking part
in the reaction.
(a) When 31 g of copper(II) carbonate is used:(I)how many grams of carbon dioxide form?(ii)what
mass of solid remains after heating?
(14)For any gas, calculate the volume at rtp of:(a) 7 moles (b) 0.5 moles (c)0.001 moles
(15)Calculate the volume at rtp of:(a)16 g of oxygen (O2) (b)1.7 g of ammonia (NH3
(16)You burn 6 grams of carbon in plenty of air: C ( s) +O2(g)-------------->CO2( g)
(a)What volume of gas will form (at rtp)?
(b) What volume of oxygen will be used up?
(17)If you burn the carbon in limited air, the reaction is
different: 2C (s)+ O2(g)-----------------> 2CO ( g)
(a)What volume of gas will form this time?
(b)What volume of oxygen will be used up
(18)How many moles of solute are in:(a) 500 cm3of solution, of concentration 2 mol / dm3? (b)2 litres
of solution, of concentration 0.5 mol / dm3?
(19) What is the concentration of a solution containing:(a)4 moles in 2 dm3of solution?(b)0.3 moles
in 200 cm3 of solution?
(20) Different solutions of salt are made up. What volume of:(a) a 4 mol / dm3 solution contains
2moles of X? (b)a 6 mol / dm3 solution contains 0.03 moles of X?
(21)The Mr of sodium hydroxide is 40. How many grams of sodium hydroxide are there in:
(a)500 cm3of a molar solution?(b)25 cm3 of a 0.5 M solution?
(20)What is the concentration in moles per litre of:(a)a sodium carbonate solution containing 53 g
of the salt (Na2CO3) in 1 litre?(b)a copper(II) sulfate solution containing 62.5 g of the salt (CuSO4.5H2O)
in 1 litre?
(23) (a) How many atoms of hydrogen combine with one carbon atom to form methane, CH4?
(b)How many grams of hydrogen combine with 12 grams of carbon to form methane?
(24)56 g of iron combine with 32 g of sulfur to form iron sulfide.Find the empirical formula for iron
sulfide.
(25)An oxide of sulfur is 40% sulfur and 60% oxygen. What is its empirical formula?
(26)In the ionic compound magnesium chloride, magnesium and chlorine atoms combine in the
ratio 1:2. What is the formula of magnesium chloride?
(27)In the ionic compound aluminium fluoride, aluminium and fluorine atoms combine in the ratio
1:3. What is the formula of aluminium fluoride?
(28)What is the difference between an empirical formula and a molecular formula? Can they ever
be the same?
(29) What is the empirical formula of benzene, C6H6?
(30)A compound has the empirical formula CH2 Its Mr is 28. What is its molecular formula?
(31)A hydrocarbon is 84% carbon, by mass. Its relative molecular mass is 100. Find:(a) its empirical
formula (b)its molecular formula
(32)An oxide of phosphorus has an Mr value of 220. It is 56.4% phosphorus. Find its molecular
formula.
(33)Define the term: a % yield b % purity
(34) 100 g of aspirin was obtained from 100 g of salicylic acid.What was the % yield?
(35)17 kg of aluminium was produced from 51 kg of aluminium oxide (Al2O3) by electrolysis.What
was the percentage yield?
(35) Some seawater is evaporated. The sea salt obtained is found to be 86% sodium chloride. How
much sodium chloride could be obtained from 200 g of this salt?
(36) A 5.0 g sample of dry ice (solid carbon dioxide) turned into 2400 cm3 of carbon dioxide gas at
rtp. What was the percentage purity of the dry ice?
(37) Iron is obtained by reducing iron(III) oxide using the gas carbon monoxide. The reaction is:
Fe2O3(s) + 3CO ( g)------------> 2Fe (s) + 3CO2( g)
(a)Write a word equation for the reaction.
(b)What is the formula mass of iron(III) oxide?
(c)How many moles of Fe2O3 are there in 320 kg of iron(III) oxide? (1 kg 51000 g.)
(d)How many moles of Fe are obtained from 1 mole of Fe2O3?
(e)From c and d, find how many moles of iron atoms are obtained from 320 kg of iron(III) oxide.
(f)How much iron (in kg) is obtained from 320 kg of iron(III) oxide?
(38)With strong heating, calcium carbonate undergoes thermal decomposition:
CaCO3(s)--------------> CaO (s) + CO2( g)
(a) How many moles of CaCO3 are in 50 g of calcium carbonate?
(b)What mass of calcium oxide is obtained from the thermal decomposition of 50 g of calcium
carbonate, assuming a 40% yield ?
(c)What mass of carbon dioxide will be given off at the same time?
(d).What volume will this gas occupy at rtp?
(39) Nitroglycerine is used as an explosive. The equation for the explosion reaction is:
4C3H5(NO3)3( l )---------->12CO2( g)+10H2O ( l )+6N2( g) +O2( g)
(a)How many moles does the equation show for: (I).nitroglycerine? (ii).gas molecules produced?
(b)How many moles of gas molecules are obtained from 1 mole of nitroglycerine?
(c)What is the total volume of gas (at rtp) obtained from 1 mole of nitroglycerine?
(d)What is the mass of 1 mole of nitroglycerine?
(e)What will be the total volume of gas (at rtp) from exploding 1 kg of nitroglycerine?
(f)Using your answers above, try to explain why nitroglycerine is used as an explosive
(40)Nitrogen monoxide reacts with oxygen like this: 2NO ( g) +O2( g)-------------->2NO2( g)
(a) How many moles of oxygen molecules react with 1 mole of nitrogen monoxide molecules?
(b) What volume of oxygen will react with 50 cm3of nitrogen monoxide?
(c) Using the volumes in b, what is:(I) the total volume of the two reactants?(Ii)the volume of nitrogen
dioxide formed?
(41)2 g (an excess) of iron is added to 50 cm3 of 0.5 M sulfuric acid. When the reaction is over, the
reaction mixture is filtered. The mass of the unreacted iron is found to be 0.6 g.
(a)What mass of iron took part in the reaction?
(b)How many moles of iron atoms took part?
(c)How many moles of sulfuric acid reacted?
(d)Write the equation for the reaction, and deduce the charge on the iron ion that formed.
(e) What volume of hydrogen (calculated at rtp) bubbled off during the reaction?
(43)27 g of aluminium burns in chlorine to form 133.5 g of aluminium chloride.
(a)What mass of chlorine is present in 133.5 g of aluminium chloride?
(b)How many moles of chlorine atoms is this?
(c)How many moles of aluminium atoms are present in 27 g of aluminium?
(d)Use your answers for parts b and c to find the simplest formula of aluminium chloride.
(e)1 dm3 of an aqueous solution is made using 13.35 g of aluminium chloride. What is its
concentration in moles per dm3?
(44) You have to prepare some 2 M solutions, with 10 g of solute in each. What volume of solution
will you prepare, for each solute below?
(a) lithium sulfate, Li2SO4 (b) magnesium sulfate, MgSO4(c) ammonium nitrate, NH4NO3
(45)Phosphorus forms two oxides, which have the empirical formulae P2O3 and P2O5
(a)Which oxide contains the higher percentage of phosphorus?
(b)What mass of phosphorus will combine with 1 mole of oxygen molecules (O2) to form P2O3?
(c)What is the molecular formula of the oxide that has a formula mass of 284?
(d)Suggest a molecular formula for the other oxide.
(46)Zinc and phosphorus react to give zinc phosphide. 9.75 g of zinc combines with 3.1 g of
phosphorus.
(a) Find the empirical formula for the compound.
(b) Calculate the percentage of phosphorus in it.
(47)110 g of manganese was extracted from 174 g of
manganese oxide.
(a)What mass of oxygen is there in 174 g of manganese oxide?
(b)How many moles of oxygen atoms is this?
(c)How many moles of manganese atoms are there in 110 g of manganese?
(d)Give the empirical formula of manganese oxide.
(e)What mass of manganese can obtained from 1000 g of manganese oxide?
(48) Hydrocarbons A and B both contain 85.7% carbon. Their molar masses are 42 and 84 g
respectively.
(a)Which elements does a hydrocarbon contain?
(b)Calculate the empirical formula of A and B.
(c)Calculate the molecular formula of A and B.
(49)Mercury(II) oxide breaks down on heating:2HgO (s)-----------> 2Hg ( l )+ O2( g)
(a)Calculate the mass of 1 mole of mercury(II) oxide
(b)How much mercury and oxygen couldbe obtained from 21.7 g of mercury(II) oxide?
(c)Only 19.0 g of mercury was collected. Calculate the % yield of mercury for this experiment.
(50) A 5-g sample of impure magnesium carbonate is reacted with an excess of hydrochloric acid:
MgCO3(s)+ 2HCl (aq)-------------> MgCl2(aq) +H2O ( l ) +CO2( g)
1250 cm3 of carbon dioxide is collected at rtp.
(a)How many moles of CO2 are produced?
(b)What mass of pure magnesium carbonate would give this volume of carbon dioxide?
(c)Calculate the % purity of the 5-g sample.
(51)An oxide of hydrogen has percentage composition by mass H=5.9% and O=94.1%.Its relative
atomic mass is 34.Calculate the molecular formula of the oxide
(52)By titration 22.5cm3 of the solution of sulphuric acid neutralizes 25cm3 of 0.1mol/dm3 solution
of sodium hydroxide .Calculate the concentration of acid.
(53)What is the concentration in mol/dm3 of a solution containing 12g of lithium hydroxide
(54)Solution Y contains 30.0 g/dm3 of FeSO 4. xH2O. In a titration, 25.0 cm3 of Y reacted with
27.0cm3 of 0.02 mol/dm3 KMnO4. In the reaction, 5 moles of FeSO4.xH2O react with 1 mole
KMnO4. Calculate the concentration of Y in mol/dm3 and the value of x
dissolved in 200cm3 of water.
(55)61g of barium chloride crystal were heated and formed 52g of the anhydrous salt.what is the
percentage by mass of the water of crystallization?
(56)30.0 cm3 of 0.100 mol/dm3 NaOH reacted completely with 25.0cm3 of H2SO4 in a
titration. Calculate the concentration of H2SO4 in mo mol/dm3 given that:
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l))
(57)25.0 cm3 of FeSO4(aq), H2SO4(ag) acidified, needs 27.5cm3 of 0.020 mol/dm3 KMnO4 for
reaction in titration. Calculate the concentration of FeSO4(aq)
(58)An acid has formula of H2XO4. One mole of H2XO4 reacts with 2 moles of NaOH. A solution of the
acid contain 5.0 g/dm3of H2XO4. In titration, 25.0cm3 of acid reacted with 25.5cm3of 0.1 mol/dm3
NaOH. Calculate the concentration of acid in mol/dm3 and find X of the acid and its identity
(59)5 g of impure sulphuric acid is dissolved in 1 dm3of water. 25.0 cm3of the solution required
23.5 cm3 of 0.1 mol/dm3 NaOH for complete titration reaction. Calculate the percentage purity of
the acid.
(60)In a titration, 25.0 cm3 of 0.04mol/dm3 H2O2 reacted with 20.0 cm3 of 0.02
mol/dm3 KMnO4. Find the values of x and y given the equation:
xH2O2 + yKMnO4 + acid → products