making salts Flashcards
2:34 know the general rules for predicting the solubility of ionic compounds in water: sodium (Na+), potassium (K+) and ammonium (NH4+)
soluble
2:34 know the general rules for predicting the solubility of ionic compounds in water: nitrates (NO3-)
soluble
2:34 know the general rules for predicting the solubility of ionic compounds in water: chlorides (Cl-)
soluble
exceptions: silver chloride (AgCl) and lead (II) chloride (PbCl2)
2:34 know the general rules for predicting the solubility of ionic compounds in water: sulfates (SO42-)
soluble
exceptions: barium sulfate (BaSO4), calcium sulfate (CaSO4) and lead (II) sulfate (PbSO4)
2:34 know the general rules for predicting the solubility of ionic compounds in water: carbonates (CO32-)
insoluble
exceptions: sodium carbonate (Na2CO3), potassium carbonate (K2CO3) and ammonium carbonate ((NH4)2CO3)
2:34 know the general rules for predicting the solubility of ionic compounds in water: hydroxides (OH-)
insoluble
exceptions: sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium hydroxide (Ca(OH)2) (calcium hydroxide is slightly soluble)
2:39 describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant
- Heat acid (H2SO4) in a beaker to speed up the rate of reaction
- Add base (CuO) until in excess (no more copper oxide dissolves) and stir with glass rod to neutralise all the acid
- Filter the mixture using filter paper and funnel to removes any excess copper oxide
- Gently heat the filtered solution (CuSO4) to evaporate some of the water until crystals form on a glass rod. this shows a hot saturated solution formed
- Allow the solution to cool so that hydrated crystals form because copper sulfate less soluble in cold solution
- Remove the crystals by filtration and dry by leaving in a warm place to evaporate the water
2:40 (Triple only) describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an acid and alkali
- Pipette 25cm3 of alkali (NaOH) into a conical flask to accurately measure the alkali (NaOH)
- Do not add indicator to prevent contamination of the pure crystals with indicator
- Using the titration values, titrate the known volume acid (HCl) into conical flask containing alkali to exactly neutralise all of the alkali (NaOH)
- Transfer to an evaporating basin & heat the solution to form a hot saturated solution (NaCl(aq))
- Allow the solution to cool so that hydrated crystals form because sodium chloride is less soluble in cold water
- Remove the crystals by filtration and wash with distilled water to remove any impurities and dry by leaving in a warm place to evaporate the water
2:33 (Triple only) describe how to carry out an acid-alkali titration
- measure 25cm of hydrochloric acid using a pipette and transfer to a conical flask
- fill burette with sodium hydroxide solution and take initial reading to 2 decimal places at eye level
- add a few drops of phenolphthalein indicator
- add sodium hydroxide in little amounts until indicator changes colour
- take burette final reading.
- repeat experiment using exactly the volume of hydrochloric acid used with no indicator.
2:41 (Triple only) describe an experiment to prepare a pure, dry sample of an insoluble salt, starting from two soluble reactants
- Mix the two salt solutions ( silver nitrate solution (AgNO3) and potassium chloride solution (KCl)) together in a beaker to form a precipitate of an insoluble salt (AgCl)
- Stir with glass rod to make sure all reactants have reacted
- Filter using filter paper and funnel to collect the precipitate (AgCl)
- Wash with distilled water to remove any the other soluble salts (KNO3)
- Dry by leaving in a warm place to evaporate the water
2:42 practical: prepare a sample of pure, dry hydrated copper(II) sulfate crystals starting from copper(II) oxide
- Heat sulfuric acid (H2SO4) in a beaker to speed up the rate of reaction
- Add base (CuO) until in excess (no more copper oxide dissolves) and stir with glass rod to neutralise all the acid
- Filter the mixture using filter paper and funnel to remove any excess copper oxide
- Gently heat the filtered solution (CuSO4) to evaporate some of the water until crystals form on a glass rod (shows a hot saturated solution formed)
- Allow the solution to cool so that hydrated crystals form because copper sulfate less soluble in cold solution
- Remove the crystals by filtration and dry by leaving in a warm place to evaporate the water
2:43 (Triple only) practical: prepare a sample of pure, dry lead(II) sulfate
- Mix similar volumes lead nitrate solution and sodium sulfate solution in a beaker. The precise volumes do not matter since any excess will be removed later.
- A white precipitate of lead (II) sulfate will form.
- The reaction mixture is filtered.
- The residue left on the filter paper is washed with distilled water several times to remove impurities.
- The residue is then moved to a warm oven to dry.
