Name: Secondary School

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1 Name: Secondary School 0

2 1 Contents ANSWERS Task 1: The structure of atoms 2 Task 2: Atoms and ions 3 Task 3: Writing formulas 4 Task 4: Relative masses 5 Task 5: Balancing equations 5 Task 6: Writing symol equations from words 7 Task 7: Using moles 8 Task 8: Reacting Mass calculations 9 Task 9: Yields and atom economy 10 Task 10: Empirical and molecular formulae 11 Task 11: Titration calculations 12 Task 12: Different types of structures 13 Task 13: Alkanes and formulae 14 Task 14: Products from fuels 15 Task 15: Fractional distillation and cracking 16

3 2 Task 1: The structure of atoms 1 Complete the spaces to create a set of notes aout the structure of atoms. Atoms consist of a central nucleus containing protons and neutrons. The nucleus is small compared to the size of the whole atom. The nucleus is surrounded y electrons in energy levels (also called shells). Atoms have no electric charge ecause they contain the same numer of protons and electrons. Su-atomic particle Relative mass Proton 1 +1 Neutron 1 0 Electron Almost zero -1 Relative charge Electrons in Atomic numer = numer of protons. Mass numer = numer of protons + numer of neutrons. mass numer 19 Symol e.g. F atomic numer 9 protons = 9 neutrons = 10 electrons = 9 Atoms of the same element have the same numer of protons. It is the numer of protons that determines what type of atom it is (e.g. all atoms with six protons are caron atoms). Atoms of different elements have different numers of protons. Isotopes are atoms of the same element. They contain the same numer of protons ut a different numer of neutrons. 2 Complete the tale aout some atoms. Atom 23 11Na Atomic numer Mass numer Numer of protons Numer of neutrons Numer of electrons Li Ar K Al Cl U U

4 3 Task 2: Atoms and ions You will need to look at the Periodic Tale to help you answer the following questions. 1 a Complete the tale to show the electronic structure of the following ions. Ion F Na + Al 3+ K + S 2 H + O 2 Ca 2+ Li + Mg 2+ Cl Be 2+ Electronic structure [2,8] - [2,8] + [2,8] 3+ [2,8,8] + [2,8,8] 2- [0]+ [2,8] 2- [2,8,8] 2+ [2] + [2,8] 2+ [2,8,8] - [2] 2+ Complete the tale elow to show the electronic structure of some Group 0 elements (nole gases).place the ions from part a into the correct row of the tale. Element Electronic structure Ions with the same electronic structure He 2 Li, Be Ne 2,8 F, Na, Al, O, Mg Ar 2,8,8 K, S, Ca, Cl c i Complete the tale with the ions from part a. Ions for Group 1 have een done for you. Do not include the H + ion. Group Ions Li + Na + K + Be 2+ Mg 2+ Ca 2+ Al 3+ O 2- S 2- F - Cl - Charge ii Predict the charge that the following ions would have using the Periodic Tale and your tale. strontium ions +2 iodide ions -1 ruidium ions +1 2 Calcium atoms react with chlorine atoms to form the ionic compound calcium chloride. Calcium atoms each lose two electrons to form calcium ions. Chlorine atoms each gain one electron to form chloride ions. This means that calcium atoms react with chlorine atoms in the ratio of one calcium atom for every two chlorine atoms. Complete the diagram to show the electronic structure of the calcium and chlorine atoms and the calcium and chloride ions. Answer in class 3 Complete the following tale aout some atoms and ions. The first row has een done for you. Particle Atom or ion Atomic numer Mass numer Numer of protons Numer of neutrons Numer of electrons Electronic structure 16 O 2 ion [2, 8] 2 31 P atom ,8,5 27 Al atom ,8,3 27 Al 3+ ion [2,8] 3+ 4 He atom S 2- Ion [2, 8, 8] 2 24 Mg 2+ ion [2, 8] 2+

5 4 Task 3: Writing formulas Use the tale of ions to write the formula of the following ionic compounds. Use the general rule of cross-multiply and then simplify where possile. Eg: Aluminium oxide: Al 3+ O 2- X3 X2 Al 2 O 3 Positive ions Negative ions aluminium Al 3+ lead P 2+ romide Br oxide O 2 ammonium NH 4 + lithium Li + caronate CO 3 2 sulfate SO 4 2 arium Ba 2+ magnesium Mg 2+ chloride Cl sulfide S 2 calcium Ca 2+ potassium K + fluoride F copper (II) Cu 2+ silver Ag + hydrogencaronate HCO 3 hydrogen H + sodium Na + hydroxide OH iron (II) Fe 2+ zinc Zn 2+ iodide I iron (III) Fe 3+ nitrate NO 3 1 a potassium iodide KI 2 a potassium sulfate K 2 SO 4 sodium oxide Na 2 O magnesium sulfate MgSO 4 c aluminium romide AlBr 3 c magnesium hydroxide Mg(OH) 2 d magnesium chloride MgCl 2 d copper (II) nitrate Cu(NO 3 ) 2 e silver oxide Ag 2 O e zinc caronate ZnCO 3 f iron (II) oxide FeO f potassium hydroxide KOH g iron (III) oxide Fe 2 O 3 g sodium caronate Na 2 CO 3 h calcium sulfide CaS h aluminium hydroxide Al(OH) 3 i copper (II) chloride CuCl 2 i ammonium hydroxide NH 4 OH j lithium fluoride LiF j ammonium chloride NH 4 Cl k arium chloride BaCl 2 k aluminium sulfate Al 2 (SO 4 ) 3 l lead sulfide PS l iron (III) nitrate Fe(NO 3 ) 3

6 5 Task 4: Relative masses Element A r Element A r Element A r aluminium Al 27 hydrogen H 1 phosphorus P 31 romine Br 80 iodine I 127 potassium K 39 calcium Ca 40 iron Fe 56 silver Ag 108 caron C 12 magnesium Mg 24 sodium Na 23 chlorine Cl 35.5 nitrogen N 14 sulfur S 32 copper Cu 63.5 oxygen O 16 zinc Zn 65 fluorine F a 58 a 55.2% % c 400 c 48.0% d 162 d 1.2% e 132 e 21.2% f f 57.7% g 286 g 16.1% h 392 h 14.3% Task 5: Balancing equations Balance the following equations. a N 2 + 3H 2 2NH 3 2Ca + O 2 2CaO c Br 2 +2KI 2KBr + I 2 d 3Fe + 4H 2 O Fe 3 O 4 + 4H 2 e C 3 H 8 + 5O 2 3CO 2 + 4H 2 O f 4NH 3 + 5O 2 4NO + 6H 2 O

7 6 Task 4: Relative masses (Fully worked solutions to prolems to follow shortly).

8 7 Task 6: Writing symol equations from words Write symol equations for the following reactions taking place. You will first need to convert the names of the materials into formulae and then alance the equation. 1. Zinc metal reacts with copper sulphate solution to produce solid copper metal and zinc sulphate solution. Zn + CuSO 4 Cu + ZnSO 4 2. Solid calcium hydroxide reacts with solid ammonium chloride on heating to produce solid calcium chloride, steam and ammonia gas. Ca(OH) 2 + 2NH 4 Cl CaCl 2 + 2H 2 O + 2NH 3 3. When lead (II) nitrate is heated in a dry test tue lead (II) oxide, nitrogen dioxide gas and oxygen are produced. 2P(NO 3 ) 2 2PO + 4NO 2 + O 2 4. Silicon tetrachloride reacts with water to produce solid silicon dioxide and hydrogen chloride gas. SiCl 4 + 2H 2 O SiO 2 + 4HCl 5. When octane (C 8 H 18 ) vapour is urned with excess air in a car engine caron dioxide and water vapour are produced. C 8 H O 2 8CO 2 + 9H 2 O (accept multiples) 6. When ruidium reacts with water a solution of the hydroxide of the metal is produced as well as hydrogen gas. 2R + 2H 2 O 2ROH +H 2 7. When strontium reacts with water a solution of the hydroxide of the metal is produced as well as hydrogen gas. Sr + 2H 2 O Sr(OH) 2 +H 2 8. Sodium chloride reacts with concentrated sulfuric acid to produce sodium hydrogen sulphate and hydrogen chloride. NaCl +H 2 SO 4 NaHSO 4 + HCl

9 8 Task 7: Using moles Element A r Element A r Element A r aluminium Al 27 hydrogen H 1 phosphorus P 31 romine Br 80 iodine I 127 potassium K 39 calcium Ca 40 iron Fe 56 silver Ag 108 caron C 12 magnesium Mg 24 sodium Na 23 chlorine Cl 35.5 nitrogen N 14 sulfur S 32 copper Cu 63.5 oxygen O 16 zinc Zn 65 fluorine F 19 1 Complete the lank parts of the following tale. Sustance Formula M r Mass Moles caron monoxide CO g 20 propane C 3 H g 0.2 unknown solid unknown g methane CH kg 375 sodium caronate Na 2 CO g 2.5 unknown gas unknown g How many moles are there in each of the following? a 72 g of Mg moles = mass = 72 M r 24 = 3 moles 39 g of Al(OH) moles c 1 tonne of NaCl moles (3s.f) d 20 mg of Cu(NO 3 ) moles (3s.f) 3 What is the mass of each of the following? a 5 moles of Cl 2 mass = M r moles = 71 5 = 355 g 0.2 moles of Al 2 O g c moles of (NH 4 ) 2 SO g d 0.3 moles of Na 2 CO 3.10H 2 O 85.8 g 4 An experiment was carried out to find the M r of vitamin C (ascoric acid). It was found that 1 g contains moles of vitamin C molecules. Calculate the M r of vitamin C. 1/ = 176 g (to 3sf)

10 9 Task 8: Reacting Mass calculations Use A r values given in task 7 for this exercise. Answer in the space provided. Show your working. 1 What mass of hydrogen is needed to react with 40 g of copper oxide? CuO + H 2 Cu + H 2 O Moles CuO = 0.503, moles H 2 = 0.503, mass H 2 = 1.01 g. 2 What mass of sulfur trioxide is formed from 96 g of sulfur dioxide? 2 SO 2 + O 2 2 SO 3 Moles SO 2 = 1.5, moles SO 3 = 1.5, mass SO 3 = 120 g 3 What mass of caron monoxide is needed to react with 480 g of iron oxide? Fe 2 O CO 2 Fe + 3 CO 2 Moles Fe 2 O 3 = 3, moles CO = 9, mass CO = 252 g. 4 What mass of oxygen is needed to react with 8.5 g of hydrogen sulfide (H 2 S)? 2 H 2 S + 3 O 2 2 SO H 2 O Moles H 2 S = 0.25, moles O 2 = 0.375, mass O 2 = 12 g 5 What mass of oxygen is required to oxidise 34 g of ammonia (NH 3 ) to nitrogen monoxide (NO)? 4 NH O 2 4 NO + 6 H 2 O Moles NH 3 = 2, moles O 2 = 2.5, mass O 2 = 80 g g of hydrated sodium sulfate crystals (Na 2 SO 4.nH 2 O) gave 2.20 g of anhydrous sodium sulfate on heating to constant mass. Work out the relative formula mass (M r ) of the hydrated sodium sulfate and the value of n. Na 2 SO 4.nH 2 O Na 2 SO 4 + n H 2 O Moles Na 2 SO 4 = , moles Na 2 SO 4.nH 2 O = , M r Na 2 SO 4.nH 2 O = 322.7, n = 10.

11 10 Task 9: Yields and atom economy % yield = mass of product otained maximum theoretical mass of product 100 Atom economy = Mr wanted product from equation total Mr of products from equation Quicklime (calcium oxide, CaO) can e made y thermal decomposition of limestone (calcium caronate, CaCO 3 ). CaCO 3 CaO + CO 2 a Calculate the maximum theoretical mass of quicklime that can e made y heating 50 g of limestone (relative atomic masses: C = 12, O = 16, Ca = 40). 28 g In the reaction, only 26 g of quicklime was produced. Calculate the percentage yield. 92.9% 2 Aluminium is made y the electrolysis of aluminium oxide. Calculate the atom economy for the production of aluminium in this reaction. (relative atomic masses: O = 16, Al = 27) 2 Al 2 O 3 4 Al + 3 O % 3 Hydrazine (N 2 H 4 ) was used as the rocket fuel for the Apollo missions to the moon. It is made y the reaction of ammonia (NH 3 ) with sodium chlorate (NaOCl) (relative atomic masses: H = 1, N = 14, O = 16, Na = 23, Cl = 35.5). ammonia + sodium chlorate hydrazine + sodium chloride + water 2 NH 3 + NaOCl N 2 H 4 + NaCl + H 2 O a Calculate the maximum theoretical mass of hydrazine that can e made y reacting 340 g of ammonia with an excess of sodium chlorate. 320 g In the reaction, only 280 g of hydrazine was produced. Calculate the percentage yield. 87.5% c Give three reasons why less than the maximum theoretical yield was produced. Reaction s reversile, some NH 3 lost separating it from the reaction mixture, other reactions take place. d Calculate the atom economy for this way of making hydrazine. 29.5%

12 11 Task 10: Empirical and molecular formulae Empirical formula is the simplest whole numer ratio of elements. Divide the percentage or mass y the Mr of each element in the compound, divide y the smallest numer and simplify to give a whole numer ratio. Element A r Element A r Element A r aluminium Al 27 hydrogen H 1 phosphorus P 31 romine Br 80 iodine I 127 potassium K 39 calcium Ca 40 iron Fe 56 silver Ag 108 caron C 12 lead P 207 sodium Na 23 chlorine Cl 35.5 magnesium Mg 24 sulfur S 32 copper Cu 63.5 nitrogen N 14 zinc Zn 65 fluorine F 19 oxygen O 16 1 Copy and complete the tale. Empirical formula M r Molecular formula CH 2 42 C 3 H 6 CH 2 70 C 5 H 10 CH 2 56 C 4 H 8 C 3 H 8 44 C 3 H 8 HO 34 H 2 O 2 CH 78 C 6 H 6 2 Find the empirical formula of each of the following sustances using the data aout composition y mass. a H 5% F 95% HF Na 3.71 g O 1.29 g Na 2 O c P 90.7% O 9.3% P 3 O 4 d C 60.0% H 13.3% O 26.7% C 3 H 8 O g of iron reacts with chlorine to form g of iron chloride. Find the empirical formula for the iron chloride. FeCl 3 4 Analysis of a compound consisting of caron, hydrogen and oxygen showed it to contain g C, g H, and g O. It has a relative formula mass (M r ) of 88. a Calculate the empirical formula of the compound. C 2 H 4 O Calculate the molecular formula of the compound. C 4 H 8 O 2

13 12 Task 11: Titration calculations TRIPLE/ FURTHER SCIENCE 1 Sodium hydroxide and hydrochloric acid react together according to the equation: NaOH + HCl NaCl + H 2 O In a titration etween sodium hydroxide solution and hydrochloric acid 25.0 cm 3 of 0.2 mol/dm 3 sodium hydroxide solution is neutralised y cm 3 of hydrochloric acid. Use the information to calculate the concentration of the hydrochloric acid in mol/dm 3. Give your answer to 2 decimal places. (3 marks) 0.18 mol/dm 3 (3 marks) 2 Potassium hydroxide and hydrochloric acid react together according to the equation: KOH + HCl KCl + H 2 O In a titration etween potassium hydroxide solution and hydrochloric acid 10.0 cm 3 of 0.1 mol/dm 3 potassium hydroxide solution is neutralised y 0.12 mol/dm 3 hydrochloric acid. Use the information to calculate the volume of hydrochloric acid needed to exactly neutralise the potassium hydroxide solution. Give your answer to 2 decimal places. (3 marks) 8.33 cm 3 (3 marks) 3 Potassium hydroxide and nitric acid react together according to the equation: KOH + HNO 3 KNO 3 + H 2 O In a titration etween potassium hydroxide solution and nitric acid 25.0 cm 3 of 0.25 mol/dm 3 potassium hydroxide solution is neutralised y 0.2 mol/dm 3 nitric acid. Use the information to calculate the volume of nitric acid needed to exactly neutralise the potassium hydroxide solution. Give your answer to 2 decimal places. (3 marks) cm 3 (3 marks)

14 13 Task 12: Different types of structures Complete the tale aout sustances with each of the types of structures shown. Type of structure Simple molecular Ionic Giant covalent Metallic Description of the structure Many separate molecules. Each molecule is made from atoms joined y covalent onds. There are weak forces etween the molecules. Many positive and negative ions. There are strong electrostatic attractions etween the positive and negative ions. A regular, giant network of atoms joined y covalent onds. Type of onding Covalent Ionic Covalent Metallic Melting and oiling points (with reason) Electrical conductivity (with reason) Low weak forces etween molecules Do not conduct molecules are neutral High strong attraction etween positive and negative ions Conducts when molten or dissolved as ions can move. Does not conduct when solid as ions cannot move around. Very high many covalent onds need to e roken Graphite conducts as it has delocalised electrons. Others do not as they do not have delocalised electrons. Exception: Graphite A regular, giant structure of positive metal ions surrounded y delocalised outer shell electrons. High strong attraction etween positive metal ions and delocalised electrons Conduct as they have delocalised electrons. Which type of sustances have this structure Some non-metal elements and compounds containing nonmetals Compounds containing metals and non-metals Diamond, graphite and silicon dioxide Metals

15 14 Task 13: Alkanes and formulae 1 a Compounds of hydrogen and caron only. (1 mark) c d Covalent ond. (1 mark) Hydrocarons containing C C onds and C H onds only. (1 mark) They only have single caron to caron onds. (1 mark) 2 a Propane molecules have three caron atoms and eight hydrogen atoms. (2 marks) The onds etween the atoms. (1 mark) 3 a One from: they take part in similar chemical reactions; the molecular formula for each successive memer differs y CH 2. (1 mark) c d C n H 2n+2 (1 mark) C 8 H 18 (1 mark) C 9 H 20 (1 mark) 4 a Single covalent onds. (1 mark) c C 4 H 10 (1 mark) It shows the onds present etween the atoms in the molecule. (1 mark) 5 a CH 4, C 2 H 6, C 3 H 8 (3 marks) Displayed formulae for the alkanes in part a. (3 marks) 6 a Four caron atoms, 10 hydrogen atoms. (1 mark) C 4 H 10 (1 mark) c Two from: it follows the general formula for the alkanes, it only has single caron to caron onds, it is a hydrocaron. (2 marks)

16 15 Task 14: Products from fuels 1 a Caron dioxide. (1 mark) Water. (1 mark) 2 Caron dioxide. (1 mark) 3 a Caron and hydrogen. (2 marks) c d Caron dioxide and water. (2 marks) Oxygen. (1 mark) paraffin wax + oxygen caron dioxide + water (2 marks) 4 a Caron (soot). (1 mark) Caron monoxide. (1 mark) 5 a Sulfur dioxide. (1 mark) Nitrogen. (1 mark) 6 a C 3 H 8 + 5O 2 3CO 2 + 4H 2 O (1 mark) c d C 3 H 8 + 3½O 2 3CO + 4H 2 O (1 mark) C 3 H 8 + 3O 2 C + 2CO + 4H 2 O (1 mark) ½N 2 + O 2 NO 2 (1 mark)

17 16 Task 15: Fractional distillation and cracking 1 Use the words from the word ox to complete these sentences. oiling distillation fractions fuel gas oil vapour The different fractions in crude oil can e separated y fractional distillation. The different fractions have different oiling points. The crude oil is turned into a gas. It travels up a fractionating column, where different fractions cool down, and the vapour turns ack into a liquid. Different fractions have different uses. For example, petrol is used as a fuel for cars. The tale elow shows how many arrels of different fractions of crude oil are produced in a day at an oil refinery. Fraction LPG petrol naphtha paraffin diesel Numer of arrels you produce Numer of arrels you can sell Which fraction can you sell more of than you produce each day? (1 mark) 3 Some arrels are left over and not sold each day. Which fraction is this? (1 mark) 4 Write a paragraph to explain what you do with the leftover arrels. Use the following words in your answer: cracked, alkanes, alkenes, fuels, plastics. (7 marks) Extension 5 Explain why cracking is useful y considering supply and demand issues. (3 marks) Answers (Q2-5) 2 Petrol. (1 mark) 3 Paraffin. (1 mark) 4 Paraffin is cracked, y passing vaporised paraffin over hot catalyst, producing shorter alkanes, used as fuels, and alkenes, used to make plastics. (7 marks) 5 Demand for petrol is greater than supply, supply of paraffin is greater than demand, surplus paraffin is cracked to make up for petrol shortfall. (3 marks)