1. Atomic structure
A section of Chemistry, 9701
Listing 10 of 359 questions
In the Periodic Table, the p block contains elements whose outer electrons are found in the psubshell. Elements in the pblock show a general increase in first ionisation energy as the atomic number increases. Draw the shape of a p orbital.  Write an equation to show the first ionisation energy of silicon. Explain why there is a general increase in first ionisation energies of the elements across Period3. ElementA is in the pblock. The graph shows the successive ionisation energies for the removal of the first ten electrons of A. number of electrons removed ionisation energy State and explain the group of the Periodic Table that element A belongs to. group number explanation  Silicon is found in many compounds in the Earth’s crust. Silicon has only three naturally occurring isotopes, 28Si, 29Si and 30Si. The table shows data for 28Si, 29Si and 30Si. 28Si 29Si 30Si relative isotopic mass 28.0 29.0 30.0 A sample of silicon contains 92.2% 28Si. The total percentage abundance of 29Si and 30Si in the sample is 7.8%. The relative atomic mass, Ar, of silicon in the sample is 28.09. Calculate the percentage abundance of 30Si. Give your answer to one decimal place.  percentage abundance of 30Si = %  Silicon reacts with nitrogen gas to form Si3N4. Si3N4 is a solid with a melting point of 1900 °C. It is insoluble in water and does not conduct electricity when molten. Suggest the type of bonding in and structure of Si3N4. Explain your answer. Sulfur-containing compounds, such as C2H5SH, are found in fossil fuels, and produce SO2 when they are burned. Write the equation to show the complete combustion of C2H5SH. State why the presence of SO2 in the atmosphere has environmental consequences. Describe one of the consequences on the environment. SO2 can react with ozone, O3, to form SO3 in two different reactions. In one reaction, SO2 reacts with O3 until a dynamic equilibrium is established. SO2+ O3SO3+ O2State and explain the effect of an increase in pressure on the composition of the equilibrium mixture. In the other reaction, a different equilibrium is established at 300 K as shown. 3SO2+ O33SO3ΔH = +462.3 kJ mol–1 Suggest a temperature needed to increase the yield of SO3 at equilibrium. Explain your answer. 
9701_w19_qp_22
THEORY
2019
Paper 2, Variant 2
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Radium is a Group2 element. The predicted lattice energy, , of radium sulfide, RaS, is –2612 kJ mol–1. Define . Some data relating to radium and sulfur are listed. Select relevant data from this list for use in your answers to parts to . process value / kJ mol–1 enthalpy change for Ra→ Ra2++ 2e– +1619 first ionisation energy of sulfur +1000 second ionisation energy of sulfur +2260 first electron affinity of sulfur –200 second electron affinity of sulfur +532 enthalpy change for S8+ 2e– → S2–+555 lattice energy of RaS–2612 Write an equation for the process corresponding to the second electron affinity of sulfur. Include state symbols. Sulfur exists as S8 molecules in the solid state. Use the data in this question to calculate the enthalpy change for the reaction S8→8S.  enthalpy change = kJ mol–1 Calculate the standard enthalpy change of formation, , of radiumsulfide.  standard enthalpy change, = kJ mol–1 State the two major factors that affect the numerical magnitude of a lattice energy. For each factor you have identified in , state whether it tends to make the lattice energy of radiumsulfide more or less exothermic than that of sodiumchloride. Explain your answer. The lattice energies of sodiumchloride, NaCl, and radiumsulfide, RaS, are –771 kJ mol–1 and –2612 kJ mol–1, respectively. Identify the dominant factor in determining the relative numerical magnitudes of the lattice energies of radiumsulfide and sodiumchloride. Explain your answer.
9701_w21_qp_42
THEORY
2021
Paper 4, Variant 2
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The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl . The first ionisation energy of S is not shown. Table 1.1 property P S Cl number of electrons in 3p subshell total number of unpaired electrons first ionisation energy / kJ mol–1 formula of most common anion P3– S2– Cl – Complete Table 1.1 to show the number of electrons in the 3p subshell and the total number of unpaired electrons in an atom of P, S and Cl . Construct an equation to represent the first ionisation energy of P. Three possible values for the first ionisation energy of S are given. 1000 kJ mol–1 1160 kJ mol–1 1320 kJ mol–1 Circle the correct value. Explain your choice by comparing your chosen value to those of P and Cl . P3–, S2– and Cl – have the same number of electrons. Give the full electronic configuration of P3–. State the trend in ionic radius shown by P3–, S2– and Cl –. Explain your answer. A student does three tests on separate samples of NaCl . Complete Table 1.2 with the observations the student makes in each test. Table 1.2 test test observations addition of a few drops of Br22 addition of a few drops of concentrated H2SO4 addition of a few drops of dilute AgNO3 POCl3 shows similar chemical properties to PCl5. POCl3 has a melting point of 1°C and a boiling point of 106 °C. POCl3 reacts vigorously with water, forming misty fumes and an acidic solution. Explain how the information in suggests the structure and bonding of POCl3 is simple covalent. Construct an equation for the reaction of POCl3 with water. POCl3 + POCl3 contains a double covalent bond between P and O. Complete the dot-and-cross diagram, in , to show the bonding in POCl3. Show outer shell electrons only. O P Cl Cl Cl POCl3forms when PCl3reacts with O2. 2PCl3+ O22POCl3Table 1.3 gives some relevant data. Table 1.3 process value / kJ mol–1 enthalpy change of formation of PCl3–289 enthalpy change of formation of POCl3–592 O22O+496 Define enthalpy change of formation, ΔHf . Calculate the bond energy of P=O in POCl 3 using the data in Table 1.3. Show your working. bond energy of P=O = kJ mol–1
9701_w23_qp_21
THEORY
2023
Paper 2, Variant 1
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The elements silicon, phosphorus and sulfur are in Period 3 of the Periodic Table. Describe the variation in atomic radius from silicon to sulfur. The melting point of silicon is 1410 °C. The melting point of sulfur is 113 °C. Explain this difference. Table 1.1 shows some properties of the elements Si to S. The first ionisation energy of P is not shown. Table 1.1 property Si P S total number of electrons in s subshells total number of electrons in p subshells first ionisation energy / kJ mol–1 formula of most common chloride SiCl 4 PCl 5 SCl 2 Complete Table 1.1 to show the total number of s and p electrons in an atom of Si, P and S. Construct an equation to represent the first ionisation energy of Si. Three possible values for the first ionisation energy of P are given. 619 kJ mol–1 893 kJ mol–1 1060 kJ mol–1 Circle the correct value. Explain your choice, including a comparison of your chosen value to those of Si and S. SiCl 4 and PCl 5 each react with water, forming misty fumes. Identify the chemical responsible for the misty fumes. Predict the shape of the SCl 2 molecule.
9701_w23_qp_22
THEORY
2023
Paper 2, Variant 2
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The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl . The first ionisation energy of S is not shown. Table 1.1 property P S Cl number of electrons in 3p subshell total number of unpaired electrons first ionisation energy / kJ mol–1 formula of most common anion P3– S2– Cl – Complete Table 1.1 to show the number of electrons in the 3p subshell and the total number of unpaired electrons in an atom of P, S and Cl . Construct an equation to represent the first ionisation energy of P. Three possible values for the first ionisation energy of S are given. 1000 kJ mol–1 1160 kJ mol–1 1320 kJ mol–1 Circle the correct value. Explain your choice by comparing your chosen value to those of P and Cl . P3–, S2– and Cl – have the same number of electrons. Give the full electronic configuration of P3–. State the trend in ionic radius shown by P3–, S2– and Cl –. Explain your answer. A student does three tests on separate samples of NaCl . Complete Table 1.2 with the observations the student makes in each test. Table 1.2 test test observations addition of a few drops of Br22 addition of a few drops of concentrated H2SO4 addition of a few drops of dilute AgNO3 POCl3 shows similar chemical properties to PCl5. POCl3 has a melting point of 1°C and a boiling point of 106 °C. POCl3 reacts vigorously with water, forming misty fumes and an acidic solution. Explain how the information in suggests the structure and bonding of POCl3 is simple covalent. Construct an equation for the reaction of POCl3 with water. POCl3 + POCl3 contains a double covalent bond between P and O. Complete the dot-and-cross diagram, in , to show the bonding in POCl3. Show outer shell electrons only. O P Cl Cl Cl POCl3forms when PCl3reacts with O2. 2PCl3+ O22POCl3Table 1.3 gives some relevant data. Table 1.3 process value / kJ mol–1 enthalpy change of formation of PCl3–289 enthalpy change of formation of POCl3–592 O22O+496 Define enthalpy change of formation, ΔHf . Calculate the bond energy of P=O in POCl 3 using the data in Table 1.3. Show your working. bond energy of P=O = kJ mol–1
9701_w23_qp_23
THEORY
2023
Paper 2, Variant 3
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Questions Discovered
359