QUESTIONSHEETS ATOMIC STRUCTURE PRINCIPLES OF MASS SPECTROMETRY RELATIVE ATOMIC MASS FROM MASS SPECTROMETRY

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1 CHEMISTRY QUESTIONSHEETS AS Level AS TOPIC 1 ATOMIC STRUCTURE Questionsheet 1 Questionsheet 2 Questionsheet 3 Questionsheet 4 Questionsheet 5 Questionsheet 6 Questionsheet 7 Questionsheet 8 Questionsheet 9 Questionsheet 10 Questionsheet 11 Questionsheet 12 Questionsheet 13 Questionsheet 14 Questionsheet 15 Questionsheet 16 Questionsheet 17 Questionsheet 18 SUBATOMIC PARTICLES RELATIVE ATOMIC MASS THE MASS SPECTROMETER PRINCIPLES OF MASS SPECTROMETRY RELATIVE ATOMIC MASS FROM MASS SPECTROMETRY FIRST IONISATION ENERGY CHANGES IN FIRST IONISATION ENERGIES ACROSS THE PERIODIC TABLE SUCCESSIVE IONISATION ENERGIES ELECTRONIC CONFIGURATIONS OF ATOMS ELECTRON AFFINITY ATOMIC RADII COMPARISIONS OF ATOMIC AND IONIC RADII IONISING RADIATIONS RADIOACTIVITY APPLICATIONS OF RADIO-ISOTOPES TEST QUESTION I TEST QUESTION II THE HYDROGEN SPECTRUM 16 marks 12 marks 13 marks 15 marks 14 marks 14 marks 13 marks 16 marks 13 marks 16 marks 20 marks 22 marks 14 marks 16 marks 16 marks 22 marks 16 marks 17 marks Authors Trevor Birt Donald E Caddy Andrew Jones Adrian Bond Editors John Brockington Stuart Barker John Brockington Kevin Frobisher Andy Shepherd Stuart Barker ress urriculum C P Curriculum Press Bank House 105 King Street Wellington Shropshire TF1 1NU Curriculum Press Licence Agreement: Paper copies of the A-Level Chemistry Questionsheets may be copied free of charge by teaching staff or students for use within their school, provided the Photocopy Masters have been purchased by their school. No part of these Questionsheets may be reproduced or transmitted, in any other form or by any other means, without the prior permission of the publisher. All rights are reserved. This license agreement is covered by the laws of England and Wales Curriculum Press March 2008.

2 TOPIC 1 Questionsheet 1 SUBATOMIC PARTICLES a) (i) Define the terms atom and element, distinguishing carefully between these two terms. Atom... [1]... Element [1] Define the term isotopes. (iii) Define the terms mass number and atomic number. Use these terms to explain the difference between the terms element and isotope. Mass number... [1] Atomic number... [1] Difference between an element and an isotope [2] b) Name the main particles found in the atomic nuclei of all elements, with the exception of an isotope of one particular element. Give the main characteristics of these particles and name the exceptional isotope. Names and characteristics [4] Exception... [1] c) Using your Periodic Table, complete the following table: Number of neutrons Number of electrons Radon Pb I - [3] TOTAL / 16

3 TOPIC 1 Questionsheet 2 RELATIVE ATOMIC MASS a) (i) Define the term relative abundance as it refers to isotopes of elements in the Earth s crust. Define the term relative atomic mass. (iii) Bromine occurs as two stable isotopes in the Earth s crust, bromine-79 and bromine-81. The relative abundances of these are 50.5% and 49.5% respectively. Use these data to calculate the relative atomic mass of bromine to one decimal place. b) (i) In quantitative chemistry, the amount of a substance is quoted as a number of moles. Define the term mole. Define the term molar mass and the write down a mathematical expression which relates this term to the number of moles and mass. Molar mass... [1] Relationship [1] (iii) How many particles are there in 15 grams of carbon-12? (Take Avogadro s number, L, to be x ) TOTAL / 12

4 AS Level TOPIC 1 Questionsheet 3 THE MASS SPECTROMETER a) Label the components of the mass spectrometer, A - F. + B C D A E F F b) (i) What are the main functions of a vacuum pump in a mass spectrometer? [6] Explain the meaning of the term mass spectrum. (iii) Explain why a chemical species must be positively charged to be detected by a mass spectrometer. TOTAL / 13

5 TOPIC 1 Questionsheet 4 PRINCIPLES OF MASS SPECTROMETRY Explain the terms ionisation, fragmentation, acceleration, deflection and detection as used in mass spectrometry. Ionisation [4] Fragmentation [4] Acceleration [3] Deflection... [1] Detection [3] TOTAL / 15

6 TOPIC 1 Questionsheet 5 RELATIVE ATOMIC MASS FROM MASS SPECTROMETRY a) The mass spectrum of a sample of gallium contains only two peaks at mass/charge ratios 69 and 71. The heights of these peaks in a mass spectrum of gallium are 145 mm and 95 mm. (i) Calculate the relative abundance of each isotope of gallium to one decimal place. Calculate the relative atomic mass of gallium to two decimal places. (iii) Why is it a good approximation to assume that the relative mass of the Ga + cations, calculated from mass spectrometry, is the same as the relative atomic mass of Ga? b) The diagram below is the mass spectrum for molecular bromine. 100 Relative Abundance / % Mass / Charge Ratio (i) Identify the chemical species responsible for each peak in the spectrum.... [4] Bromine occurs in the Earth s crust as two stable isotopes with approximately 50% relative abundance. Why are the peaks corresponding to mass/charge ratios of 79 and 81 of similar height? (iii) Explain why the heights of the triplet of peaks at mass/charge ratio 158, 160 and 162 are in the ratio 1 : 2: 1. TOTAL / 14

7 TOPIC 1 Questionsheet 6 FIRST IONISATION ENERGY a) Define the term first ionisation energy and write an equation to represent the first ionisation energy of chlorine. Definition [4] Equation... [2] b) Give the name of the enthalpy change occurring in the following process:- Mn 3+ (g) Mn 4+ (g) + e -... [1] c) State whether the process in b) is exothermic or endothermic and explain your choice. d) State and explain the trend in first ionisation energies down a group of the Periodic Table.... [4] TOTAL / 14

8 TOPIC 1 Questionsheet 7 CHANGES IN FIRST IONISATION ENERGIES ACROSS THE PERIODIC TABLE a) State and explain the general trend in first ionisation energies across a period of s-block and p-block elements. b) Statement 1 Between Groups 2 and 3 and between Groups 5 and 6 this overall trend is contravened. (i) Using electron-in-box notation, draw the electron configurations of beryllium and boron and, also, the configurations of the chemical species which are formed when the first ionisation occurs. [2] Using electron-in-box notation, draw the electron configurations of nitrogen and oxygen and, also, the configurations of the chemical species formed when the first ionisation occurs. (iii) Using the diagrams you have given, explain Statement 1. [2]... [6] TOTAL / 13

9 TOPIC 1 Questionsheet 8 SUCCESSIVE IONISATION ENERGIES Consider the first eight successive ionisation energies for three elements. Element Successive ionisation energies / kj mol -1 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th 8 th X Y Z a) Suggest to which group in the Periodic Table each element belongs. Give the reasons for your choice.... [5] b) Place the atoms in order of increasing atomic number. c) X is from the third period. Suggest its identity and use the data to sketch the shape of a graph of logarithm (successive ionisation energy) versus number of electrons removed. Identity of X... [1] lg I No. of electrons removed [3] d) On your graph indicate from which sub-shell each electron is removed. [2] e) Explain what could be deduced about the electronic energy levels in a sodium atom from inspection of the 11 successive ionisation energies of this element. TOTAL / 16

10 TOPIC 1 Questionsheet 9 ELECTRONIC CONFIGURATIONS OF ATOMS a) Information is summarised for the s-block element, sodium, in the following table. Complete the table for the other species. Element Electronic configuration Block Sodium 1s 2 2s 2 2p 6 3s 1 s Calcium ion, Ca 2+ Silicon Sulfide, S 2- b) With the aid of labelled diagrams, describe the three dimensional shape of the following atomic orbitals: (i) an s atomic orbital Description... Diagram [6] [2] a p y atomic orbital Description... Diagram c) Place the following orbitals in ascending order of energy, starting with a 1s orbital. 1s, 3p, 5d, 4s, 4f, 6p, 4p, 5s, 2p, 3d. [2] TOTAL / 13

11 TOPIC 1 Questionsheet 10 ELECTRON AFFINITY a) (i) Explain the meaning of the term first electron affinity with reference to oxygen. Write an equation for the process by which second electron affinity of oxygen is defined. (iii) State whether the first and second electron affinities of oxygen are exothermic or endothermic or neither. Explain your statement. First electron affinity [2] Second electron affinity [2] b) (i) Suggest how and why the values of the electron affinities down Group 7 in the Periodic Table vary from chlorine to iodine. Predict, giving your reasons, whether the first electron affinity of sulphur is greater or smaller than the first electron affinity of chlorine. (iii) The electron affinity of fluorine is said to be anomalous when compared with the rest of the Group 7 elements. What does this statement mean and why is it so? TOTAL / 16

12 H TOPIC 1 Questionsheet 11 ATOMIC RADII He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar a) Explain what is meant by the terms shielding, nuclear charge and effective nuclear charge. Shielding... Nuclear charge... Effective nuclear charge... b) Use these terms to explain the following trends. (i) Variation of atomic radii across a period of s- and p-block elements in the Periodic Table. Variation of atomic radii down a group of elements in the Periodic Table. c) For each of the following pairs of atoms, state which has the larger radius. Explain your choice. (i) Argon atom and potassium atom Sodium atom and magnesium atom Quality of language [1] TOTAL / 20

13 TOPIC 1 Questionsheet 12 COMPARISONS OF ATOMIC AND IONIC RADII For each of the following pairs of chemical species, state which has the larger radius. Explain your choice. a) Na and Cl [3] b) Na + and Rb +... c) Mg and Mg d) Cl and Cl -... e) H + and H -... f) O - and O g) N 3- and Mg Quality of language [1] TOTAL / 22

14 TOPIC 1 Questionsheet 13 IONISING RADIATIONS a) (i) Complete the following table Radiation Nature of radiation Relative penetrative power Alpha Thin sheet of paper Emission of electrons Gamma [5] Using a labelled sketch, describe how each of these forms of radiation is affected by an electrical field created between two electrodes. b) (i) Suggest why the occurrence of lung cancer can be higher than the national average in some communities living in stone houses, and name the element concerned. [5] The particular isotopes concerned are alpha emitters, which have very limited penetrating power. Explain why they cause lung cancer, especially. TOTAL / 14

15 TOPIC 1 Questionsheet 14 RADIOACTIVITY a) (i) What is meant by the term radio-isotope?... [1] Define the term half-life of a radionuclide.... [1] (iii) Write a balanced equation for the decay of thorium-228 by emission of alpha radiation. (iv) Write a balanced equation for the decay of radium-228 by emission of beta radiation. (v) Thorium-232 can decay to thorium-228 in three steps. Suggest a possible route, giving a balanced nuclear equation for each step.... [4] b) (i) Radon-222 is radioactive but almost chemically inactive. Explain this statement. Radon-222 undergoes alpha emission with a half-life of 3 days and 20 hours. What percentage of a sample of radon-222 will remain after 19 days and 4 hours? (iii) The half-life of radon-220 is 52 seconds. Approximately, how long will it take to decay to 6.25% of its original mass? TOTAL / 16

16 TOPIC 1 Questionsheet 15 APPLICATIONS OF RADIO-ISOTOPES a) Carbon from a sample of an ancient relic from an archaeological investigation gave a reading on a radiation counter of 7.5 counts per minute. Fresh wood gave a reading of 15 counts per minute. How long ago would you deduce the sample was made? Give any assumptions you would make. Age of sample... Assumptions... b) Name a radio-isotope which is used in medicine and briefly outline its application. c) (i) Explain, using a sketch, how a radioactive source can be used to control the thickness of the sheet steel from a rolling mill. Sketch Explanation [4] What properties of a radio-isotope would you consider in selecting the best radio-isotope for this function? Explain your choice.... [5] TOTAL / 16

17 TOPIC 1 Questionsheet 16 TEST QUESTION I a) Naturally occurring sulphur contains 95.0% sulfur-32, 0.76% sulfur-33 and 4.2% sulfur-34. (i) Complete the following table. Sulfur Sulfur-33 Number of protons Number of neutrons Number of electrons Sulfur-34 [3] Write down the symbols of these three isotopes, taking care that the atomic number and mass number of each are shown in their correct positions. (iii) Use the data in a) (i) to calculate the relative atomic mass of sulfur to 4 significant figures. b) (i) The addition of a neutron to the nucleus of an atom would have the following effect on the element: increase the atomic mass True? False? increase the atomic number True? False? alter the chemical properties True? False? Different isotopes of the same elements differ in their atomic masses True? False? atomic numbers True? False? chemical properties True? False? c) (i) What are the differences between 1 H 2 O and 1 H 2 O 2? [3] [3] What are the differences between 1 H 2 O and 2 H 2 O? (iii) What are the differences between 12 CO and 14 CO 2? TOTAL / 22

18 TOPIC 1 Questionsheet 17 TEST QUESTION II a) Element X has an atomic number of 9. Figure 1 shows its mass spectrum and Figure 2 is a graph of its successive lg ionisation energies. Figure 1 Figure 2 lg I Relative abundance Mass/charge ratio No. of electrons removed (i) Write down the electronic configuration of the element X.... [1] To which group of the Periodic Table does X belong?... [1] (iii) What is the relative atomic mass of X?... [1] (iv) In what way is the isotopic composition of X unusual?... [1] (v) Write down the formulae of the species which account for the two peaks shown in Figure 1. (vi) How do you account for the shape of the graph shown in Figure 2? TOTAL (Continued...) /

19 TOPIC TOPIC 1 Questionsheet 1 Questionsheet 17 Continued 18 TEST QUESTION II b) Element Y has the electronic configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 1. (i) To which group of the Periodic Table does Y belong?... [1] Y has a relative atomic mass of 69.7, and consists of a mixture of two isotopes of mass numbers 69 and 71 respectively. On the axes of Figure 3, sketch the mass spectrum you would expect for element Y. Figure 3 Relative abundance Mass/charge ratio [2] (iii) On the axes of Figure 4, sketch the graph you would expect for successive lg ionisation energies of element Y. Lg I Figure No. of electrons removed [3] c) Write down the likely formula of a compound which could be formed between X and Y.... [1] TOTAL / 16

20 TOPIC 1 1 Questionsheet 1819 THE HYDROGEN SPECTRUM a) Explain why the hydrogen spectrum provides evidence for the existence of fixed energy levels for electrons in atoms.... [4] b) In the context of the hydrogen spectrum, chemists refer to convergence towards a series limit. (i) What is meant by convergence?... [1] In which direction is there convergence? (iii)... [1] Explain why convergence occurs in the direction you have stated in b) [3] c) The complete hydrogen spectrum comprises more than just the Balmer series in the visible region of the electromagnetic spectrum. There is also the Lyman series in the ultraviolet region and the Paschen (and other) series in the infrared. State how Lyman series arises, and explain why it occurs in the ultraviolet Cause... [1] Explanation... [1] d) (i) Explain the connection between the ionisation energy of hydrogen and radiation emitted at the series limit of the Lyman series [2] Given the wavelength or frequency of radiation at the series limit of the Lyman series, name two constants which you would require in order to calculate the ionisation energy of hydrogen [2] TOTAL (Continued...) /

21 TOPIC TOPIC 1 Questionsheet 1 Questionsheet 18 Continued 20 THE HYDROGEN SPECTRUM e) The energy levels for atomic hydrogen are shown in the diagram below (only 1-5 and? are shown for clarity n = n = 5 n = 4 n = 3 C D G F n = 2 A B E n = 1 The emission spectrum of atomic hydrogen is shown below (some lines are omitted for clarity) Frequency Ionisation energy In the table below match the numbers of the lines with the letters of the transitions Spectrum line Energy level transition [4] TOTAL / 17