12.5. Identification of ions and gases
A subsection of Chemistry, 0620, through 12. Experimental techniques and chemical analysis
Listing 10 of 359 questions
The table shows the masses of some of the ions in 1000 cm3 of fruit juice. name of ion formula of ion mass of ion in 1000 cm3 of fruit juice / mg ammonium NH4 + calcium Ca2+ chloride Cl – magnesium Mg2+ NO3 – phosphate PO4 3– potassium K+ Na+ sulfate SO4 2– Answer these questions using only the information in the table. State which negative ion has the highest mass in 1000 cm3 of fruit juice. Give the formulae of the ions in sodium nitrate. and Calculate the mass of ammonium ions in 250 cm3 of fruit juice.  mass = mg Describe a test for chloride ions. test observations  Phosphate ions, PO4 3–, are present in most fertilisers. Phosphate ions contain phosphorus. State the names of two other elements that are in most fertilisers.  Explain why farmers put fertilisers on fields where crops are to be grown. A student heated ammoniumsulfate with sodiumhydroxide in a test-tube. Complete the equation for this reaction. (NH4)2SO4 + NaOH → NH3 + Na2SO4 + 2H2O Concentrated aqueous ammonia releases fumes of ammonia gas. A long glass tube is set up as shown. long glass tube cotton wool soaked in concentrated aqueous ammonia damp red litmus paper At first, the red litmus paper does not turn blue. After a short time, the litmus paper turns blue. Explain these observations using the kinetic particle model. 
0620_s21_qp_33
THEORY
2021
Paper 3, Variant 3
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Sodiumhydrogencarbonate is found in baking powder. When sodiumhydrogencarbonate is heated it forms three products. 2NaHCO3 → Na2CO3 + H2O + CO2 Name the type of reaction that takes place when sodiumhydrogencarbonate reacts in this way. Calculate the volume of carbondioxide formed at room temperature and pressure when 12.6 g of NaHCO3 is heated using the following steps: ● determine the mass of one mole of NaHCO3  g ● calculate the number of moles of NaHCO3 used  moles ● determine the number of moles of carbon dioxide formed  moles ● calculate the volume of carbon dioxide formed at room temperature and pressure.  dm3  Limewater is aqueous calcium hydroxide. Carbon dioxide turns limewater milky because a white precipitate forms. Write the formula of: ● calcium hydroxide ● the white precipitate that forms when limewater turns milky.  
0620_s21_qp_42
THEORY
2021
Paper 4, Variant 2
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This question is about salts. Salts that are soluble in water can be made by the reaction between insoluble carbonates and dilute acids. Zincsulfate is soluble in water. You are provided with solid zinc carbonate, ZnCO3, and dilute sulfuric acid, H2SO4. Describe how you would make a pure sample of zincsulfate crystals. Your answer should include: ● practical details ● how you would make sure that all the dilute sulfuric acid has reacted ● a chemical equation for the reaction. Some sulfates decompose when heated. When hydrated iron(sulfate is heated strongly, sulfurdioxide gas is given off. Describe a test for sulfurdioxide. test observations  Complete the equation for the decomposition of hydrated iron(sulfate. FeSO4•7H2O → Fe2O3 + SO2 + SO3 + H2O Some chlorides are hydrated. When hydrated bariumchloride crystals, BaCl 2•xH2O, are heated they give off water. BaCl 2•xH2O→ BaCl 2+ xH2OA student carries out an experiment to determine the value of x in BaCl 2•xH2O. step 1 Hydrated bariumchloride crystals are weighed. step 2 The hydrated bariumchloride crystals are then heated. step 3 The remaining solid is weighed. Describe how the student can be sure that all the water is given off. In an experiment, 4.88 g of BaCl 2•xH2O is heated until all the water is given off. The mass of BaCl 2 remaining is 4.16 g. [Mr: BaCl 2, 208; H2O, 18] Determine the value of x using the following steps. ● Calculate the number of moles of BaCl 2 remaining.  mol ● Calculate the mass of H2O given off.  g ● Calculate the number of moles of H2O given off.  mol ● Determine the value of x.  x =  
0620_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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