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carbonates, although carbonates also release carbon dioxide."},{"text":"A substance that releases hydrogen ions, such as hydrochloric, sulfuric or nitric acid.","correct":false,"explanation":"Releasing hydrogen ions describes an acid, not a base. A base neutralises an acid and may be a metal oxide, hydroxide or carbonate."},{"text":"A substance that dissolves a salt, such as water, ethanol or propanone.","correct":false,"explanation":"This describes the role of a solvent rather than a base. A base is a substance that neutralises an acid to form a salt."},{"text":"A substance that speeds up a reaction, such as iron, nickel or platinum.","correct":false,"explanation":"Speeding up a reaction without being consumed describes a catalyst. A base instead neutralises an acid, producing a salt during salt preparation."}]},{"id":"6fbbeb06-74e0-4bae-8636-67c3d449df34","cardType":"basic","points":1,"front":"What does insoluble mean?","back":"A substance that does not dissolve, or dissolves only very slightly, in a particular solvent.","mcqOptions":[{"text":"A substance that does not dissolve, or dissolves only very slightly, in a particular solvent.","correct":true,"explanation":"Solubility depends on the solute and solvent involved; an insoluble substance either does not dissolve or dissolves only to a very small extent."},{"text":"A substance that dissolves completely and rapidly in a particular solvent.","correct":false,"explanation":"Dissolving completely describes a soluble substance, while speed of dissolving is not the definition. Insoluble substances dissolve either not at all or only very slightly."},{"text":"A substance that does not react, or reacts only very slowly, with a particular solvent.","correct":false,"explanation":"Solubility concerns whether a substance dissolves, not whether it chemically reacts. An insoluble substance does not dissolve, or dissolves only very slightly, in the solvent."},{"text":"A substance that settles out only after becoming saturated in a particular solvent.","correct":false,"explanation":"Crystals may form from a saturated solution, but that does not define insolubility. An insoluble substance dissolves either not at all or only very slightly."}]},{"id":"614cb77f-a632-45ba-9572-e9ce09659258","cardType":"basic","points":1,"front":"How can a soluble salt be made from an acid?","back":"React the acid with an insoluble base, such as a metal oxide, hydroxide or carbonate.","mcqOptions":[{"text":"React the acid with an insoluble base, such as a metal oxide, hydroxide or carbonate.","correct":true,"explanation":"An insoluble base neutralises the acid, and any base added beyond the amount required can then be removed easily by filtration."},{"text":"React the acid with a soluble alkali, such as sodium hydroxide, potassium hydroxide or ammonia.","correct":false,"explanation":"A soluble alkali cannot be removed by filtration if added in excess, so this preparation requires titration. Using an insoluble base allows the excess to be filtered off."},{"text":"React the acid with an insoluble metal, such as copper, silver or gold.","correct":false,"explanation":"Copper, silver and gold are below hydrogen in the reactivity series and do not generally react with dilute acids. An insoluble base is used instead."},{"text":"React the acid with an insoluble salt, such as silver chloride, barium sulfate or calcium carbonate.","correct":false,"explanation":"Silver chloride and barium sulfate do not neutralise acids, while calcium carbonate is specifically a base. The general method requires an insoluble base."}]},{"id":"aad126db-37b5-4ffe-938e-b99b30639acc","cardType":"basic","points":2,"front":"Why is the insoluble base added in excess?","back":"Add the base in excess so that all the acid reacts.","mcqOptions":[{"text":"Add the base in excess so that all the acid reacts.","correct":true,"explanation":"Adding more insoluble base than required ensures that no acid remains; the unreacted solid base can subsequently be separated from the salt solution."},{"text":"Add the base in small portions so that none of the acid reacts.","correct":false,"explanation":"Small portions help control the reaction, but the goal is not to prevent neutralisation. Excess base is added so that all the acid reacts."},{"text":"Add the base in exact proportions so that all the water evaporates.","correct":false,"explanation":"Neutralisation does not require all water to evaporate, and exact proportions are unnecessary with an insoluble base. Excess ensures complete reaction of the acid."},{"text":"Add the base in limited amounts so that some of the acid remains.","correct":false,"explanation":"Leaving acid unreacted would contaminate the salt solution. The insoluble base is added in excess to ensure that all the acid is neutralised."}]},{"id":"d6ae0f44-5702-4d9b-8b36-6958b39e9bb9","cardType":"basic","points":2,"front":"Why can excess base be filtered off after the reaction?","back":"The excess base is insoluble, so it can be removed by filtration.","mcqOptions":[{"text":"The excess base is insoluble, so it can be removed by filtration.","correct":true,"explanation":"Because the excess base remains as solid particles rather than dissolving, filter paper traps it while the dissolved salt solution passes through."},{"text":"The excess base is volatile, so it can be removed by filtration.","correct":false,"explanation":"Volatile substances evaporate readily, which does not make them filterable. The base can be filtered off because it is an insoluble solid."},{"text":"The excess base is soluble, so it can be removed by filtration.","correct":false,"explanation":"A soluble base would pass through filter paper with the solution and could not be removed this way. Filtration works because the excess base is insoluble."},{"text":"The excess base is neutral, so it can be removed by filtration.","correct":false,"explanation":"Whether a substance is neutral does not determine whether filtration removes it. The unreacted base is trapped because it is an insoluble solid."}]},{"id":"7e415d4e-2ff0-40df-a1e6-15770247d97b","cardType":"basic","points":1,"front":"Which base reacts with sulfuric acid to make copper sulfate?","back":"The black base is copper(II) oxide.","mcqOptions":[{"text":"The black base is copper(II) oxide.","correct":true,"explanation":"Copper(II) oxide is a black, insoluble base that neutralises sulfuric acid to produce copper sulfate solution and water."},{"text":"The black base is copper(II) hydroxide.","correct":false,"explanation":"Copper(II) hydroxide can make copper sulfate but is a blue solid, not the black base described. The black reactant is copper(II) oxide."},{"text":"The black base is copper(II) carbonate.","correct":false,"explanation":"Copper(II) carbonate also reacts with sulfuric acid, but it is green and releases carbon dioxide. The black base used here is copper(II) oxide."},{"text":"The black base is magnesium oxide.","correct":false,"explanation":"Magnesium oxide would form magnesium sulfate rather than copper sulfate and is white. Copper(II) oxide is the black base needed to supply copper ions."}]},{"id":"188e4d21-f7bb-435e-ac9b-05a929273f25","cardType":"basic","points":1,"front":"Which acid reacts with copper(II) oxide to make copper sulfate?","back":"The acid used is dilute sulfuric acid.","mcqOptions":[{"text":"The acid used is dilute sulfuric acid.","correct":true,"explanation":"Sulfuric acid supplies the sulfate ions needed for copper sulfate, while copper(II) oxide supplies the copper ions and neutralises the acid."},{"text":"The acid used is dilute hydrochloric acid.","correct":false,"explanation":"Hydrochloric acid supplies chloride ions and would produce copper(II) chloride, not copper sulfate. Dilute sulfuric acid supplies the required sulfate ions."},{"text":"The acid used is dilute nitric acid.","correct":false,"explanation":"Nitric acid supplies nitrate ions and would produce copper(II) nitrate. Copper sulfate preparation requires dilute sulfuric acid as the sulfate source."},{"text":"The acid used is dilute ethanoic acid.","correct":false,"explanation":"Ethanoic acid would supply ethanoate ions rather than sulfate ions. Dilute sulfuric acid is required to form copper sulfate from copper(II) oxide."}]},{"id":"6e28c0a4-ab15-4030-9a8c-6a4802e2aaf6","cardType":"basic","points":1,"front":"Write the equation for copper(II) oxide reacting with sulfuric acid.","back":"$$$\\text{CuO}(s) + \\text{H}_2\\text{SO}_4(aq) \\rightarrow \\text{CuSO}_4(aq) + \\text{H}_2\\text{O}(l)$$","mcqOptions":[{"text":"$$$\\text{CuO}(s) + \\text{H}_2\\text{SO}_4(aq) \\rightarrow \\text{CuSO}_4(aq) + \\text{H}_2\\text{O}(l)$$","correct":true,"explanation":"Copper(II) oxide neutralises sulfuric acid to form copper sulfate and water; the equation is balanced with one atom or formula unit of each reactant."},{"text":"$$$\\text{CuO}(s) + 2\\text{HCl}(aq) \\rightarrow \\text{CuCl}_2(aq) + \\text{H}_2\\text{O}(l)$$","correct":false,"explanation":"This is the balanced reaction with hydrochloric acid and produces copper(II) chloride. Sulfuric acid instead forms copper sulfate and water."},{"text":"$$$\\text{CuO}(s) + \\text{H}_2\\text{SO}_4(aq) \\rightarrow \\text{CuSO}_3(aq) + \\text{H}_2\\text{O}(l)$$","correct":false,"explanation":"Writing sulfite instead of sulfate changes the product and leaves the oxygen atoms unbalanced. The salt formed is $\\text{CuSO}_4$, copper sulfate."},{"text":"$$$\\text{CuO}(s) + \\text{H}_2\\text{SO}_4(aq) \\rightarrow \\text{Cu}(s) + \\text{SO}_4(aq) + \\text{H}_2\\text{O}(l)$$","correct":false,"explanation":"Neutralisation does not produce copper metal or a free sulfate species. Copper(II) ions combine with sulfate ions to form aqueous copper sulfate."}]},{"id":"108ac917-5e10-4bd4-a8a8-040ae526158a","cardType":"basic","points":2,"front":"What observation shows that all the acid has reacted?","back":"The acid is fully reacted when some solid copper(II) oxide remains unreacted.","mcqOptions":[{"text":"The acid is fully reacted when some solid copper(II) oxide remains unreacted.","correct":true,"explanation":"Persistent copper(II) oxide shows that more base is present than the remaining acid can neutralise, so all the acid has been used up."},{"text":"The acid is fully reacted when all the solid copper(II) oxide has disappeared.","correct":false,"explanation":"If every piece of copper(II) oxide dissolves, acid may still remain and more base should be added. Unreacted solid confirms that the acid is fully neutralised."},{"text":"The acid is fully reacted when some blue copper sulfate crystals remain unreacted.","correct":false,"explanation":"Copper sulfate crystals are the desired product, not the base used to test for remaining acid. Unreacted solid copper(II) oxide shows that neutralisation is complete."},{"text":"The acid is fully reacted when the copper sulfate solution becomes colourless.","correct":false,"explanation":"Copper sulfate solution is blue because it contains hydrated copper(II) ions, so becoming colourless is not the endpoint. Remaining solid copper(II) oxide indicates completion."}]},{"id":"f8148c04-a925-48a8-bdb9-f69c4cf024c6","cardType":"basic","points":2,"front":"What does filtration separate in this preparation?","back":"Filtration separates the insoluble excess base from the salt solution.","mcqOptions":[{"text":"Filtration separates the insoluble excess base from the salt solution.","correct":true,"explanation":"Filter paper retains the particles of unreacted insoluble base as residue, while the aqueous copper sulfate passes through as the filtrate."},{"text":"Filtration separates the dissolved excess acid from the salt solution.","correct":false,"explanation":"Dissolved acid would pass through filter paper with the salt solution and cannot be separated by filtration. The method prevents this by adding excess insoluble base."},{"text":"Filtration separates the soluble salt crystals from the salt solution.","correct":false,"explanation":"At this stage the salt is dissolved, so it passes through the filter. Filtration removes the solid, insoluble excess base from the solution."},{"text":"Filtration separates the evaporated water vapour from the salt solution.","correct":false,"explanation":"Filtration separates an insoluble solid from a liquid, not vapour from a solution. Here it removes the excess insoluble base."}]},{"id":"5710af91-e52f-4283-b2c0-9c2072ef7d4b","cardType":"basic","points":3,"front":"What are the residue and filtrate when preparing copper sulfate?","back":"The residue is excess copper(II) oxide; the filtrate is copper sulfate solution.","mcqOptions":[{"text":"The residue is excess copper(II) oxide; the filtrate is copper sulfate solution.","correct":true,"explanation":"The insoluble copper(II) oxide is trapped on the filter paper as residue, while dissolved copper sulfate passes through in the filtrate."},{"text":"The residue is copper sulfate solution; the filtrate is excess copper(II) oxide.","correct":false,"explanation":"This reverses the filtration terms: residue stays on the filter paper, whereas filtrate passes through. Therefore, copper(II) oxide is the residue and copper sulfate solution is the filtrate."},{"text":"The residue is excess sulfuric acid; the filtrate is copper sulfate crystals.","correct":false,"explanation":"Excess base ensures no sulfuric acid remains, and dissolved salt has not yet crystallised. The residue is copper(II) oxide and the filtrate is copper sulfate solution."},{"text":"The residue is copper sulfate crystals; the filtrate is dilute sulfuric acid.","correct":false,"explanation":"Crystals form later during evaporation and cooling, while all acid should already be neutralised. Filtration leaves copper(II) oxide residue and copper sulfate solution filtrate."}]},{"id":"8c539dff-ca2f-452d-9954-6cd6a511d950","cardType":"basic","points":2,"front":"Why is some water evaporated from the salt solution?","back":"Evaporate some water until the solution becomes saturated and crystals begin forming.","mcqOptions":[{"text":"Evaporate some water until the solution becomes saturated and crystals begin forming.","correct":true,"explanation":"Removing some solvent increases the copper sulfate concentration until saturation is reached, allowing crystals to begin forming as the concentrated solution cools."},{"text":"Evaporate some water until the solution becomes dilute and crystals begin forming.","correct":false,"explanation":"Evaporation makes a solution more concentrated, not more dilute. Water is removed until the solution is saturated, enabling crystals to form."},{"text":"Evaporate some water until the solution becomes neutral and crystals begin forming.","correct":false,"explanation":"Neutrality concerns pH and is established by the earlier reaction, not evaporation. Water is evaporated to make the salt solution saturated."},{"text":"Evaporate some water until the solution becomes insoluble and crystals begin forming.","correct":false,"explanation":"A solution itself is not described as insoluble. Evaporation concentrates the dissolved salt until the solution becomes saturated and crystallisation can begin."}]},{"id":"a9270a00-ec34-4a21-8c8c-73fd6d8d9ccf","cardType":"basic","points":2,"front":"Why does crystallisation begin when the solution becomes saturated?","back":"A saturated solution contains as much dissolved salt as it can hold, so further water loss causes crystallisation.","mcqOptions":[{"text":"A saturated solution contains as much dissolved salt as it can hold, so further water loss causes crystallisation.","correct":true,"explanation":"At saturation, the solvent cannot retain additional dissolved salt under those conditions, so removing more water forces some salt to form solid crystals."},{"text":"A saturated solution contains no dissolved salt at all, so further water loss causes neutralisation.","correct":false,"explanation":"A saturated solution contains the maximum dissolved salt, not none, and water loss is not neutralisation. Further water loss forces dissolved salt to crystallise."},{"text":"A saturated solution contains as much dissolved acid as it can hold, so further water loss causes filtration.","correct":false,"explanation":"The acid has already reacted, and saturation here refers to dissolved salt. Water loss causes salt crystals to form; filtration is a separate physical process."},{"text":"A saturated solution contains as much dissolved salt as it can hold, so further water loss causes decomposition.","correct":false,"explanation":"Ordinary concentration does not chemically decompose copper sulfate. Once saturation is reached, further removal of water causes the excess dissolved salt to crystallise."}]},{"id":"ea9d798e-9d68-44cd-9b3a-3f9522f3f07f","cardType":"basic","points":2,"front":"Why is the solution cooled slowly rather than evaporated quickly to dryness?","back":"Slow cooling produces larger, purer crystals than fast evaporation to dryness.","mcqOptions":[{"text":"Slow cooling produces larger, purer crystals than fast evaporation to dryness.","correct":true,"explanation":"Slow cooling gives dissolved ions time to arrange into an orderly crystal lattice, while impurities are more likely to remain in the surrounding solution."},{"text":"Slow cooling produces smaller, less pure crystals than fast evaporation to dryness.","correct":false,"explanation":"This reverses the effect of cooling rate. Rapid crystallisation tends to trap impurities and form small crystals, whereas slow cooling produces larger, purer crystals."},{"text":"Slow cooling produces more concentrated acid than fast evaporation to dryness.","correct":false,"explanation":"The acid has already been neutralised, so cooling is not intended to concentrate it. Slow cooling allows larger, purer salt crystals to grow."},{"text":"Slow cooling produces finer insoluble powder than fast evaporation to dryness.","correct":false,"explanation":"The aim is to grow an ordered crystalline solid, not an insoluble powder. Slow cooling gives larger, purer copper sulfate crystals."}]},{"id":"4f81d1fa-baa1-4fef-8c67-dd182d4d6787","cardType":"basic","points":2,"front":"Why are copper sulfate crystals dried by patting them with filter paper?","back":"Patting with filter paper removes surface water without dissolving the crystals.","mcqOptions":[{"text":"Patting with filter paper removes surface water without dissolving the crystals.","correct":true,"explanation":"Filter paper absorbs liquid clinging to the outside of the crystals, drying them without adding a solvent that could dissolve the copper sulfate."},{"text":"Patting with filter paper removes water of crystallisation without dissolving the crystals.","correct":false,"explanation":"Water of crystallisation is chemically incorporated into hydrated copper sulfate and is not removed by patting. Filter paper removes only liquid surface water."},{"text":"Patting with filter paper removes copper sulfate ions without dissolving the crystals.","correct":false,"explanation":"Removing copper and sulfate ions would destroy or dissolve the crystals. Filter paper instead absorbs surface water while leaving the crystal lattice intact."},{"text":"Patting with filter paper removes insoluble copper oxide without dissolving the crystals.","correct":false,"explanation":"Copper(II) oxide was removed earlier by filtration and should not coat the crystals. Patting at the end removes surface water from the crystals."}]},{"id":"12eaf37a-e84d-4190-93a9-aacc3b3bba3f","cardType":"basic","points":2,"front":"Why must the salt solution not be evaporated completely to dryness?","back":"Evaporating to dryness can cause strong heating, which may spoil the crystals.","mcqOptions":[{"text":"Evaporating to dryness can cause strong heating, which may spoil the crystals.","correct":true,"explanation":"Once the solvent has gone, the solid can become strongly heated; this may drive off water of crystallisation or decompose the salt and spoil its crystals."},{"text":"Evaporating to dryness can cause rapid cooling, which may spoil the crystals.","correct":false,"explanation":"Evaporation requires heating rather than causing rapid cooling. The danger is that the dry salt becomes strongly heated and its crystals may be damaged."},{"text":"Evaporating to dryness can cause acid neutralisation, which may spoil the crystals.","correct":false,"explanation":"Neutralisation has already occurred between the acid and base before evaporation. Complete evaporation risks strongly heating and damaging the salt crystals."},{"text":"Evaporating to dryness can cause base filtration, which may spoil the crystals.","correct":false,"explanation":"Filtration is a separate step used earlier to remove excess base. Evaporating all the water instead risks strong heating that can spoil the crystals."}]},{"id":"4ffe7bb0-2183-424f-99eb-e72cd1673f96","cardType":"basic","points":2,"front":"Why is the filtrate heated on a water bath?","back":"A water bath provides gentle heating and avoids overheating the crystals.","mcqOptions":[{"text":"A water bath provides gentle heating and avoids overheating the crystals.","correct":true,"explanation":"Indirect heating limits the temperature and evaporates the water gently. This reduces the risk of vigorous boiling, spitting, or heating the solution to complete dryness."},{"text":"A water bath provides intense heating and boils the solution as quickly as possible.","correct":false,"explanation":"A water bath is used for gentle, indirect heating rather than intense boiling. Controlled evaporation prevents spitting and avoids overheating the copper sulfate crystals."},{"text":"A water bath cools the filtrate rapidly and dissolves any crystals that have formed.","correct":false,"explanation":"The filtrate is heated to evaporate some water, not cooled or used to dissolve crystals. A water bath supplies gentle heat and prevents overheating."},{"text":"A water bath removes the unreacted solid and produces a clear salt solution.","correct":false,"explanation":"Unreacted copper(II) oxide is removed by filtration, not by heating. The water bath gently concentrates the filtrate while reducing the risk of overheating."}]},{"id":"05f580d8-bd7f-49cd-ad32-6c5c3acefcf2","cardType":"basic","points":1,"front":"How much dilute sulfuric acid is used in the copper sulfate investigation?","back":"Measure 40 $\\text{cm}^3$ of dilute sulfuric acid into a beaker.","mcqOptions":[{"text":"Measure 40 $\\text{cm}^3$ of dilute sulfuric acid into a beaker.","correct":true,"explanation":"The specified method begins with 40 cubic centimetres of dilute sulfuric acid. Measuring this volume into a beaker provides the required amount for the investigation."},{"text":"Measure 20 $\\text{cm}^3$ of dilute sulfuric acid into a beaker.","correct":false,"explanation":"This halves the specified acid volume, so it does not follow the required practical method. The investigation uses 40 cubic centimetres of dilute sulfuric acid."},{"text":"Measure 50 $\\text{cm}^3$ of dilute sulfuric acid into a beaker.","correct":false,"explanation":"This likely comes from rounding to a familiar measuring-cylinder capacity, but it exceeds the specified volume. The method requires 40 cubic centimetres of dilute sulfuric acid."},{"text":"Measure 80 $\\text{cm}^3$ of dilute sulfuric acid into a beaker.","correct":false,"explanation":"This doubles the required volume and would unnecessarily increase the quantities and hazards involved. The investigation specifies 40 cubic centimetres of dilute sulfuric acid."}]},{"id":"539163eb-bfd0-480a-9938-537275a3b5bb","cardType":"basic","points":2,"front":"How is excess copper(II) oxide added to the hot acid?","back":"Add copper(II) oxide a little at a time and stir until some solid remains unreacted.","mcqOptions":[{"text":"Add copper(II) oxide a little at a time and stir until some solid remains unreacted.","correct":true,"explanation":"Adding small portions with stirring allows each portion to react. Persistent unreacted solid shows that all the sulfuric acid has been neutralised and the base is in excess."},{"text":"Add copper(II) oxide all at once and stir until all the solid has completely dissolved.","correct":false,"explanation":"Adding everything at once makes the reaction harder to control, while complete dissolution suggests the acid may remain in excess. Small portions are added until some solid remains."},{"text":"Add copper(II) oxide a little at a time and stop as soon as the first portion dissolves.","correct":false,"explanation":"Stopping after one portion dissolves leaves sulfuric acid unneutralised. Copper(II) oxide must be added gradually with stirring until some excess solid no longer reacts."},{"text":"Add copper(II) oxide after cooling the acid and stir until no solid remains unreacted.","correct":false,"explanation":"The oxide is added to the hot acid so the reaction proceeds readily, and some solid must remain to demonstrate excess base. It is then removed by filtration."}]},{"id":"689473d4-d444-4397-8566-54b667a25a4c","cardType":"basic","points":2,"front":"What safety precautions are required during this preparation?","back":"Wear eye protection and take care around the hot acid and apparatus.","mcqOptions":[{"text":"Wear eye protection and take care around the hot acid and apparatus.","correct":true,"explanation":"Eye protection guards against splashes of dilute sulfuric acid, while careful handling reduces the risk of burns from the heated solution, beaker, and heating equipment."},{"text":"Wear heatproof gloves and handle the hot acid and apparatus without eye protection.","correct":false,"explanation":"Heatproof gloves do not protect the eyes from acid splashes, so omitting goggles is unsafe. Eye protection is required alongside careful handling of hot acid and apparatus."},{"text":"Wear eye protection and hold the hot beaker directly with bare hands.","correct":false,"explanation":"Goggles protect against splashes but do not prevent burns from hot glassware. Eye protection and careful handling of the hot acid and apparatus are both required."},{"text":"Wear eye protection and heat the acid rapidly until it begins to spit.","correct":false,"explanation":"Rapid heating can cause hot acid to spit, creating splash and burn hazards despite the goggles. The acid should be heated gently and the hot apparatus handled carefully."}]},{"id":"ea96cf6f-68ff-43fb-9c5a-1ca63863ebdd","cardType":"cloze","points":null,"front":"To prepare a soluble salt, react an acid with an [ ].","back":"To prepare a soluble salt, react an acid with an insoluble base.","mcqOptions":[{"text":"insoluble base","correct":true,"explanation":"An insoluble base neutralises the acid to form a salt and water. Excess base can then be removed by filtration, ensuring no unreacted acid remains."},{"text":"insoluble acid","correct":false,"explanation":"Reacting an acid with another acid does not carry out neutralisation or supply the required positive ions. The acid should react with an insoluble base."},{"text":"inert solid","correct":false,"explanation":"An inert solid does not react with the acid, so it cannot neutralise it or form the desired salt. An insoluble base is required."},{"text":"unreactive oxide","correct":false,"explanation":"An unreactive oxide would not neutralise the acid, even though many metal oxides are bases. The method specifically requires an insoluble base that reacts with the acid."}]},{"id":"d585aea0-7fcc-40c1-9d59-07dcfdcd3205","cardType":"cloze","points":null,"front":"The insoluble excess base remains on the filter paper as the [ ].","back":"The insoluble excess base remains on the filter paper as the residue.","mcqOptions":[{"text":"residue","correct":true,"explanation":"The residue is the insoluble material retained by the filter paper. Here, it consists of excess base that did not react with the acid."},{"text":"filtrate","correct":false,"explanation":"The filtrate is the liquid that passes through the filter paper, not the solid left behind. The retained excess base is called the residue."},{"text":"precipitate","correct":false,"explanation":"A precipitate is an insoluble solid formed during a reaction in solution. Here, the solid was deliberately added in excess and is therefore the residue."},{"text":"solute","correct":false,"explanation":"A solute is a substance dissolved in a solvent, whereas the excess base remains insoluble. The solid trapped on the filter paper is the residue."}]},{"id":"2e34367d-6b55-45cf-bf49-dcb4db344524","cardType":"cloze","points":null,"front":"The liquid passing through the filter paper is called the [ ].","back":"The liquid passing through the filter paper is called the filtrate.","mcqOptions":[{"text":"filtrate","correct":true,"explanation":"The filtrate is the liquid that passes through the filter paper during filtration. It contains the dissolved copper sulfate while excess copper(II) oxide is retained."},{"text":"residue","correct":false,"explanation":"The residue is the insoluble solid trapped on the filter paper, not the liquid passing through it. That collected liquid is called the filtrate."},{"text":"solvent","correct":false,"explanation":"A solvent is the liquid in which a solute dissolves, such as water in this solution. The liquid collected after filtration is the filtrate."},{"text":"precipitate","correct":false,"explanation":"A precipitate is an insoluble solid produced in a reaction, so it does not describe the collected liquid. Liquid passing through filter paper is the filtrate."}]},{"id":"dd565256-d2ab-4209-9004-b4de4db6b9f3","cardType":"cloze","points":null,"front":"The blue solution contains dissolved [ ].","back":"The blue solution contains dissolved copper sulfate.","mcqOptions":[{"text":"copper sulfate","correct":true,"explanation":"Copper(II) oxide reacts with sulfuric acid to produce copper sulfate and water. The copper sulfate is soluble, so it remains dissolved in the blue filtrate."},{"text":"copper nitrate","correct":false,"explanation":"Copper nitrate would be produced using nitric acid, not sulfuric acid. Sulfuric acid reacts with copper(II) oxide to form dissolved copper sulfate."},{"text":"copper chloride","correct":false,"explanation":"Copper chloride would require hydrochloric acid as the acid reactant. Using sulfuric acid supplies sulfate ions, so the dissolved salt is copper sulfate."},{"text":"copper oxide","correct":false,"explanation":"Copper(II) oxide is the insoluble black base added to the acid and any excess is filtered off. The blue solution contains dissolved copper sulfate."}]},{"id":"c295a338-84e6-44ca-9600-5ab698f35ade","cardType":"cloze","points":null,"front":"Copper sulfate crystals grow slowly after the solution is left to cool for about [ ].","back":"Copper sulfate crystals grow slowly after the solution is left to cool for about a day.","mcqOptions":[{"text":"a day","correct":true,"explanation":"Leaving the concentrated solution undisturbed for about a day allows it to cool slowly and gives copper sulfate particles enough time to form visible crystals."},{"text":"a minute","correct":false,"explanation":"One minute is far too short for slow cooling and substantial crystal growth. The concentrated copper sulfate solution is normally left undisturbed for about a day."},{"text":"ten minutes","correct":false,"explanation":"Ten minutes may begin cooling the solution, but it is not the specified time for growing clear crystals slowly. The solution should be left for about a day."},{"text":"an hour","correct":false,"explanation":"An hour is shorter than the required crystallisation period and may produce only limited crystal growth. The method leaves the solution to cool for about a day."}]}]}],"examCountdown":{"examDate":"2027-05-17","paperLabel":"Paper 1"},"heading":"4.2.3 Soluble salts","title":"4.2.3 Soluble salts Flashcards","topbar":{"backHref":"/gcse/chemistry/aqa/flashcards"},"topicSidebar":"$L36"}]}],"topicId":"3ba48137-84d9-5931-b3dd-3cd1021694b2","walled":"$L37"}],"$L38","$L39"]