12.5. Identification of ions and gases
A subsection of Chemistry, 0620, through 12. Experimental techniques and chemical analysis
Listing 10 of 359 questions
A student wanted to make some zincchloride crystals. The student followed the procedure shown. step 1 Add excess zinc powder to dilute hydrochloricacid to form aqueous zincchloride. step 2 Remove unreacted zinc powder from the aqueous zincchloride. step 3 Heat the solution until it is saturated. step 4 Allow the saturated solution to cool and remove the crystals that form. Write the equation for the reaction in step1. Include state symbols. Explain why excess zinc powder is added in step1. Suggest how unreacted zinc powder is removed in step2. A saturated solution is formed in step3. Suggest what is meant by the term saturated solution. Explain why crystals form as the solution cools in step4. Name two zinc compounds which react with dilute hydrochloricacid to form zincchloride. If excess calcium metal is used instead of excess zinc powder in step1, pure calciumchloride crystals do not form. Explain why. Some salts can be made by titration. In a titration experiment, 20.0 cm3 of aqueous sodiumhydroxide reacts exactly with 25.0 cm3 of 0.100 mol / dm3 dilute sulfuricacid to make sodium sulfate. 2NaOH+ H2SO4→ Na2SO4+ 2H2OCircle the name of the type of reaction that takes place. decomposition neutralisation precipitation reduction  Calculate the concentration of the aqueous sodiumhydroxide in g / dm3 using the following steps. ● Calculate the number of moles of dilute sulfuricacid used.  mol ● Determine the number of moles of sodium hydroxide which react with the dilute sulfuricacid.  mol ● Calculate the concentration of the aqueous sodiumhydroxide in mol / dm3.  mol / dm3 ● Calculate the concentration of the aqueous sodiumhydroxide in g / dm3.  g / dm3  
0620_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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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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Questions Discovered
359