9.2. Periodicity of chemical properties of the elements in Period 3
A subsection of Chemistry, 9701, through 9. The Periodic Table: chemical periodicity
Listing 10 of 224 questions
In a world with a rapidly increasing population, access to clean drinking water is critical. For many countries, groundwater sources, rather than stored rainwater or river-water, are vital. Groundwater is water that exists in the pore spaces and fractures in rock and sediment beneath the Earth's surface. The World Health Organisation (WHO) provides maximum recommended concentrations for different ions present in drinking water. The geological nature of the soil determines the chemical composition of the groundwater. The table shows some ions which may contaminate groundwater. ion present WHO maximum permitted concentration / mg dm–3 Ba2+ 0.30 Cl – 250.00 NO3 – 50.00 Pb2+ 0.01 Na+ 20.00 SO4 2– 500.00 Nitrate, NO3 –, ions are diffi cult to remove from groundwater. What is the reason for this? State which ions in the table above are likely to be removed from the water by treatment with powdered limestone, CaCO3, giving reasons for each of your answers. Nitrates and phosphates can enter water courses such as rivers or streams as a result of human activity. Both of these ions are nutrients for algae. What is the origin of these nitrates? Suggest an origin for the phosphates found in water courses. What effect do nitrates and phosphates have on water courses? Acid rain can have a major impact on natural waters, particularly lakes. In recent years there has been a worldwide effort to reduce the amount of acid rain produced. Write equations to show the production of acid rain from sulfur dioxide, SO2. The use of fossil fuels is one major source of sulfur dioxide. Name another major industrial source.
9701_w13_qp_42
THEORY
2013
Paper 4, Variant 2
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Define the term standard cell potential. Draw a fully labelled diagram of the experimental set‑up you could use to measure the standard electrode potential of the Pb2+/ Pbelectrode. Include the necessary chemicals. The E o for a Pb2+/ Pbelectrode is – 0.13 V. Suggest how the E for this electrode would differ from its E o value if the concentration of Pb2+ions is reduced. Indicate this by placing a tick () in the appropriate box in the table. more negative no change less negative Explain your answer. Car batteries are made up of rechargeable lead-acid cells. Each cell consists of a negative electrode made of Pb metal and a positive electrode made of PbO2. The electrolyte is H2SO4. When a lead-acid cell is in use, Pb2+ ions are precipitated out as PbSO4at the negative electrode. Pb+ SO4 2–PbSO4+ 2e– Calculate the mass of Pb that is converted to PbSO4 when a current of 0.40 A is delivered by the cell for 80 minutes. mass of Pb = g Complete the half-equation for the reaction taking place at the positive electrode. PbO2+ SO4 2–+ + PbSO4+ The diagrams show how the voltage across two different cells changes with time when each cell is used to provide an electric current. voltage / V time / hours lead-acid cell voltage / V time / hours H2 / O2 fuel cell Suggest a reason why ● the voltage of the lead-acid cell changes after several hours, ● the voltage of the fuel cell remains constant.
9701_w17_qp_41
THEORY
2017
Paper 4, Variant 1
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Define the term standard cell potential. Draw a fully labelled diagram of the experimental set‑up you could use to measure the standard electrode potential of the Pb2+/ Pbelectrode. Include the necessary chemicals. The E o for a Pb2+/ Pbelectrode is – 0.13 V. Suggest how the E for this electrode would differ from its E o value if the concentration of Pb2+ions is reduced. Indicate this by placing a tick () in the appropriate box in the table. more negative no change less negative Explain your answer. Car batteries are made up of rechargeable lead-acid cells. Each cell consists of a negative electrode made of Pb metal and a positive electrode made of PbO2. The electrolyte is H2SO4. When a lead-acid cell is in use, Pb2+ ions are precipitated out as PbSO4at the negative electrode. Pb+ SO4 2–PbSO4+ 2e– Calculate the mass of Pb that is converted to PbSO4 when a current of 0.40 A is delivered by the cell for 80 minutes. mass of Pb = g Complete the half-equation for the reaction taking place at the positive electrode. PbO2+ SO4 2–+ + PbSO4+ The diagrams show how the voltage across two different cells changes with time when each cell is used to provide an electric current. voltage / V time / hours lead-acid cell voltage / V time / hours H2 / O2 fuel cell Suggest a reason why ● the voltage of the lead-acid cell changes after several hours, ● the voltage of the fuel cell remains constant.
9701_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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X, Y and Z are elements all found within Groups 13, 14 and 15 of the Periodic Table. X is in the same group in the Periodic Table as Y. Y and Z are in Period 3. The first ionisation energy of X is greater than the first ionisation energy of Y. The melting point of Z is less than the melting point of Y. Y and Z both form chlorides which are white solids. These white solids react with water to produce solutions with a pH of less than 4. Which row of the table shows the possible identities of X and Y?
9701_w23_qp_11
MCQ
2023
Paper 1, Variant 1
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X, Y and Z are elements all found within Groups 13, 14 and 15 of the Periodic Table. X is in the same group in the Periodic Table as Y. Y and Z are in Period 3. The first ionisation energy of X is greater than the first ionisation energy of Y. The melting point of Z is less than the melting point of Y. Y and Z both form chlorides which are white solids. These white solids react with water to produce solutions with a pH of less than 4. Which row of the table shows the possible identities of X and Y?
9701_w23_qp_13
MCQ
2023
Paper 1, Variant 3
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