12. Experimental techniques and chemical analysis
A section of Chemistry, 0620
Listing 10 of 677 questions
A student adds excess large pieces of magnesiumcarbonate, MgCO3, to dilute hydrochloricacid, HCl, and measures the volume of carbondioxide gas, CO2, given off. Add the missing state symbols to the chemical equation for the reaction. MgCO3 + 2HCl → MgCl 2+ H2O + CO2  Complete the dot-and-cross diagram to show the electron arrangement of the ions in magnesiumchloride. The inner shells have been drawn. Give the charges on the ions. Mg Cl Cl  Complete the dot-and-cross diagram to show the electron arrangement in a molecule of carbondioxide. Show outer shell electrons only. C O O  The graph shows how the volume of carbondioxide gas changes with time. volume of carbon dioxide gas time Describe how the graph shows that the rate of this reaction decreases as time increases. Explain, in terms of particles, why the rate of this reaction decreases as time increases. The student repeats the experiment using powdered MgCO3 instead of large pieces. All other conditions stay the same. On the grid, draw the line expected when powdered MgCO3 is used instead of large pieces. Determine the volume of CO2 gas given off when excess MgCO3 is added to 25.0 cm3 of 0.400 mol / dm3 HCl at room temperature and pressure. MgCO3 + 2HCl → MgCl 2 + H2O + CO2 Use the following steps. ● Calculate the number of moles of HCl in 25.0 cm3 of 0.400 mol / dm3 of acid.  mol ● Determine the number of moles of CO2 gas given off.  mol ● Calculate the volume of CO2 gas given off in cm3.  cm3  
0620_m22_qp_42
THEORY
2022
Paper 4, Variant 2
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A sample of soil is shaken with distilled water. Draw a diagram to show the filtration apparatus used to separate the soil from the solution obtained by shaking the soil with distilled water. On your diagram, label: ● the filtrate ● the residue.  Table2.1 shows the masses of some of the ions in 1000 cm3 of the solution obtained by filtering a sample of soil with distilled water. Table2.1 name of ion formula of ion mass of ion in 1000 cm3 of solution / mg ammonium NH4 + 25.0 calcium Ca2+ 0.4 chloride Cl – 0.5 iron(Fe2+ 27.0 magnesium Mg2+ 4.0 nitrate NO3 – 23.0 phosphate PO4 3– 15.5 potassium K+ 29.0 sodium Na+ 2.0 SO4 2– 6.0 Answer these questions using the information in Table2.1. Name the negative ion that has the lowest concentration. State the name of the SO4 2– ion. Calculate the mass of phosphate ions in 200 cm3 of the solution.  mass = mg Complete Fig.2.1 to show: ● the electronic configuration of a sodium ion ● the charge on the ion. Na  Water from natural sources contains dissolved gases. Choose from the list the gas which is essential for aquatic life. Draw a circle around your chosen answer. argon hydrogen nitrogen oxygen Polluted water may contain sewage or nitrates. State one harmful effect of each of these water pollutants. sewage nitrates  
0620_m23_qp_32
THEORY
2023
Paper 3, Variant 2
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Table2.1 shows the masses of some of the ions in a 1000 cm3 sample of river water. Table 2.1 name of ion formula of ion mass of ion in 1000 cm3 of river water / mg NH4 + 0.4 calcium Ca2+ 1.4 chloride Cl – 0.1 hydrogencarbonate HCO3 – 1.2 magnesium Mg2+ 0.6 nitrate NO3 – 0.8 phosphate PO4 3– 1.3 sodium Na+ 0.5 SO4 2– 0.4 Answer these questions using the information in Table2.1. Name the negative ion that has the highest concentration. Name the compound that contains NH4 + and SO4 2– ions only. Calculate the mass of hydrogencarbonate ions in 200 cm3 of river water.  mass = mg Give a test for sodium ions. test observations  Most of the nitrate ions in river water come from fertilisers used on fields. Describe the benefit of using fertilisers. Water from natural sources can be polluted with harmful substances. State why sewage and phosphates in river water are harmful. sewage phosphates  River water can contain acids such as ethanoic acid and methylbutanoic acid. Draw the displayed formula for ethanoic acid.  Ethanoic acid reacts with sodium hydroxide. Complete the word equation for this reaction. ethanoic acid + sodium hydroxide → +  Methylbutanoic acid has the molecular formula C5H10O2. Complete Table 2.2 to calculate the relative molecular mass of C5H10O2. Table 2.2 atom number of atoms relative atomic mass carbon 5 × 12 = 60 hydrogen oxygen  relative molecular mass = 
0620_m24_qp_32
THEORY
2024
Paper 3, Variant 2
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This question is about acids, bases and alkalis. Table 3.1 shows the pH values of some substances. Table 3.1 substance pH NaOH14 Ca(OH)210 H2O7 CH3COOH4 HNO31 Define the term base. State what is meant by the term alkali. Thymolphthalein is an indicator. State the colour of thymolphthalein in: ● NaOH● CH3COOH.  Use the information in Table 3.1 to identify the substance with the highest concentration of H+ions. Explain your answer. substance explanation  Name an indicator which can be used to identify the substance with the highest concentration of H+ions. Complete the equation to show the dissociation of ethanoic acid, CH3COOH, in aqueous solution. CH3COOHWrite the ionic equation which represents a neutralisation reaction between any acid and any alkali. Dilute nitric acid, HNO3, reacts with aqueous calcium hydroxide, Ca(OH)2, as shown. 2HNO3+ Ca(OH)2→ Ca(NO3)2+ 2H2O20.0 cm3 of 0.0150 mol / dm3 Ca(OH)2reacts with 25.0 cm3 of HNO3. Calculate the concentration of HNO3in g / dm3. Use the following steps. ● Calculate the number of moles of Ca(OH)2used.  mol ● Determine the number of moles of HNO3which react with the Ca(OH)2.  mol ● Calculate the concentration of HNO3in mol / dm3.  mol / dm3 ● Calculate the concentration of HNO3in g / dm3.  g / dm3  
0620_m24_qp_42
THEORY
2024
Paper 4, Variant 2
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