11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
Washing soda is hydrated sodium carbonate, Na2CO3.xH2O. A student wished to determine the value of x by carrying out a titration, with the following results. 5.13 g of washing soda crystals were dissolved in water and the solution was made up to 250 cm3 in a standard volumetric fl ask. 25.0 cm3 of this solution reacted exactly with 35.8 cm3 of 0.100 mol dm–3 hydrochloric acid and carbon dioxide was produced. Write a balanced equation for the reaction between Na2CO3 and HCl . Calculate the amount, in moles, of HCl in the 35.8 cm3 of solution used in the titration. Use your answers to and to calculate the amount, in moles, of Na2CO3 in the 25.0 cm3 of solution used in the titration. Use your answer to to calculate the amount, in moles, of Na2CO3 in the 250 cm3 of solution in the standard volumetric fl ask. Hence calculate the mass of Na2CO3 present in 5.13 g of washing soda crystals. Use your calculations in to determine the value of x in Na2CO3.xH2O.
9701_s12_qp_23
THEORY
2012
Paper 2, Variant 3
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Piperine is the compound responsible for the hot taste of black pepper. O N O O piperine Piperine is an amide and can be broken down as follows: O N HN O O piperine O OH + O O piperic acid piperidine Suggest reagents and conditions for this reaction. How many stereoisomers are there with the same structural formula as piperic acid (including piperic acid itself)? Draw the skeletal structure of a stereoisomer of piperic acid, different to the one shown above. Suggest structures for the compounds that would be formed when piperic acid is treated with an excess of hot concentrated acidifi ed KMnO4. Write the expression for Kw. Use your expression and the value of Kw in the Data Booklet to calculate the pH of 0.150 mol dm–3 NaOH. The pH of a 0.150 mol dm–3 solution of piperidine is 11.9. HN piperidine Suggest why this answer differs from your answer in . How would you expect the basicity of piperidine to compare to that of ammonia? Explain your reasoning. 20.0 cm3 of 0.100 mol dm–3 HCl was slowly added to a 10.0 cm3 sample of 0.150 mol dm–3 piperidine. The pH was measured throughout the addition. Calculate the number of moles of HCl remaining at the end of the addition. moles of HCl = Hence calculate the [H+] and the pH at the end of the addition. pH = On the following axes, sketch how the pH will change during the addition of a total of 20.0 cm3 of 0.100 mol dm–3 HCl. Mark clearly where the end point occurs. volume HCl added / cm3 pH From the following list of indicators, put a tick in the box by the side of the indicator most suitable for this titration. indicator pH at which colour changes place one tick only in this column A 0 - 1 B 3 - 4 C 11 - 12 D 13 - 14
9701_s14_qp_41
THEORY
2014
Paper 4, Variant 1
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Piperine is the compound responsible for the hot taste of black pepper. O N O O piperine Piperine is an amide and can be broken down as follows: O N HN O O piperine O OH + O O piperic acid piperidine Suggest reagents and conditions for this reaction. How many stereoisomers are there with the same structural formula as piperic acid (including piperic acid itself)? Draw the skeletal structure of a stereoisomer of piperic acid, different to the one shown above. Suggest structures for the compounds that would be formed when piperic acid is treated with an excess of hot concentrated acidifi ed KMnO4. Write the expression for Kw. Use your expression and the value of Kw in the Data Booklet to calculate the pH of 0.150 mol dm–3 NaOH. The pH of a 0.150 mol dm–3 solution of piperidine is 11.9. HN piperidine Suggest why this answer differs from your answer in . How would you expect the basicity of piperidine to compare to that of ammonia? Explain your reasoning. 20.0 cm3 of 0.100 mol dm–3 HCl was slowly added to a 10.0 cm3 sample of 0.150 mol dm–3 piperidine. The pH was measured throughout the addition. Calculate the number of moles of HCl remaining at the end of the addition. moles of HCl = Hence calculate the [H+] and the pH at the end of the addition. pH = On the following axes, sketch how the pH will change during the addition of a total of 20.0 cm3 of 0.100 mol dm–3 HCl. Mark clearly where the end point occurs. volume HCl added / cm3 pH From the following list of indicators, put a tick in the box by the side of the indicator most suitable for this titration. indicator pH at which colour changes place one tick only in this column A 0 - 1 B 3 - 4 C 11 - 12 D 13 - 14
9701_s14_qp_43
THEORY
2014
Paper 4, Variant 3
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Atoms and ions of elements are made up from the three subatomic particles, protons, electrons and neutrons, in varying amounts. Complete the following table to show the number of each particle in 14C2–. protons electrons neutrons 14C2– Describe the observations you would make during the reactions, if any, of the following chlorides with water. Write equations for any reactions that occur. CCl 4 observation equation GeCl 4 observation equation SnCl 4 observation equation Suggest a reason for any difference in the reactivities of the chlorides given in . Use data from the Data Booklet to explain why an aqueous solution of SnCl 2 reacts with Cl 2but an aqueous solution of PbCl 2 does not. Write an equation for the reaction. State the relationship between the Faraday constant and the Avogadro constant. When a current of 1.2 A was passed through dilute sulfuric acid for 30 minutes, it was found that 130 cm3 of oxygen, measured at 25 °C and 1 atm, was collected at the anode. The following reaction takes place. 2H2O→ 4H++ O2+ 4e– Use these data and data from the Data Booklet to calculate a value for the Avogadro constant, L, by calculating • the number of moles of oxygen produced, • the number of moles of electrons needed for this, • the number of coulombs passed, • the number of electrons passed, • the number of electrons in one mole of electrons (L). L = mol–1
9701_s15_qp_41
THEORY
2015
Paper 4, Variant 1
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Atoms and ions of elements are made up from the three subatomic particles, protons, electrons and neutrons, in varying amounts. Complete the following table to show the number of each particle in 14C2–. protons electrons neutrons 14C2– Describe the observations you would make during the reactions, if any, of the following chlorides with water. Write equations for any reactions that occur. CCl 4 observation equation GeCl 4 observation equation SnCl 4 observation equation Suggest a reason for any difference in the reactivities of the chlorides given in . Use data from the Data Booklet to explain why an aqueous solution of SnCl 2 reacts with Cl 2but an aqueous solution of PbCl 2 does not. Write an equation for the reaction. State the relationship between the Faraday constant and the Avogadro constant. When a current of 1.2 A was passed through dilute sulfuric acid for 30 minutes, it was found that 130 cm3 of oxygen, measured at 25 °C and 1 atm, was collected at the anode. The following reaction takes place. 2H2O→ 4H++ O2+ 4e– Use these data and data from the Data Booklet to calculate a value for the Avogadro constant, L, by calculating • the number of moles of oxygen produced, • the number of moles of electrons needed for this, • the number of coulombs passed, • the number of electrons passed, • the number of electrons in one mole of electrons (L). L = mol–1
9701_s15_qp_43
THEORY
2015
Paper 4, Variant 3
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Questions Discovered
617