Chemistry for 14 -16 year olds: Acids bases and salts.

Slide 1 : 1 GCSE Questions and Answers Acids, Bases and Salt Preparations 6 consecutive papers: 2002-7 There is a video-cast on this here Remember that you can search using “edit”!

Slide 2 : 2 Hydrochloric Acid Hydrochloric Acid HCl Sulphuric Acid H2SO4 Nitric Acid HNO3 Strong Mineral Acids OTHERS Lactic acid in milk, tannic acid in tea and methanoic acid in nettles and ant stings

Slide 3 : 3

Slide 4 : 4 Bases. Chemicals that neutralise acids, forming a salt. Metal Oxides, Metal Hydroxides, Metal Carbonates, Metal Hydrogencarbonates and Ammonia are bases. Alkalis. These are soluble bases.

Slide 5 : 5 Special comments about an ammonia solution. Ammonia is a gas at room temperature. 1000 cm3 of ammonia gas will dissolve in just 1 cm3 of water. The “Fountain Experiment” is used to demonstrate the high solubility of ammonia in water. [More details on the next slide.] A small percentage of the dissolved Ammonia molecules react with water molecules to form Ammonium Hydroxide. NH3 (aq) + H2O (l) ? NH4OH (aq) An ammonia solution may therefore be Labelled: NH3 (aq) or NH4OH (aq) Creation of the HYDROXIDE IONS (OH-) MAKES IT ALKALINE

Slide 6 : 6 The “Fountain Experiment” Set up as shown. Add a few of water from the dropper and release the clip to start it. Ammonia dissolves rapidly and the pressure drops inside the flask. Water is sucked up from the beaker below. A fountain is produced. The indicator changes to pink as it meets the NH3 The flask quickly fills with water.

Slide 7 : 7

Slide 8 : 8 Neither Acid nor Alkali - NEUTRAL If a solution is neither acidic nor alkaline we say that it is a NEUTRAL solution. Pure water and alcohol are neutral, as are solutions of table salt and sugar.

Slide 9 : The pH Scale is Used to Measure the Strength of Acids and Alkalis

Slide 10 : 10 Litmus indicator solution appears violet in distilled water If acid is added to the water Litmus indicator turns red. If alkali is added to the water Litmus indicator turns blue

Slide 11 : 11 Universal Indicator. Universal Indicator is a mixture of different dyes. Like your red cabbage indicator, it can change through a whole range of colours (not just one colour in acid and another in alkali). We can then match these colours to numbers on a chart. The numbers will tell us how strongly or weakly acidic or alkaline a solution is. This is called the pH scale. You can see it below, together with some interesting pH values for things we encounter in everyday life.

Slide 12 : 12 UI Colour/pH Chart Making Red Cabbage Indicator

Slide 13 : 13 Red Cabbage Indicator. A Colour/pH Chart Might also use beetroot.

Slide 14 : 14

Slide 15 : When acids and alkalis react together they will NEUTRALISE each other. Neutralisation Acid (pH less than 7) Alkali (pH more than 7) +

Slide 16 : When acids and alkalis react together they will NEUTRALISE each other. Neutralisation Neutral (pH 7)

Slide 17 : 17

Slide 18 : 18 SOME NEUTRALISATIONS IN EVERYDAY LIFE

Slide 19 : 19 Indigestion It may surprise you to know that you carry hydrochloric acid around in your stomach. You need it for digesting food. But too much of it leads to indigestion, which can be very painful. To cure indigestion, you must neutralise the excess acid with a drink of sodium hydrogen carbonate solution (baking soda), or an indigestion tablet.

Slide 20 : 20 Soil Treatment Most plants grow best when the pH of the soil is close to 7. If the soil is too acidic, or too alkaline, the plants grow badly or not at all. Chemicals can be added to soil to adjust its pH. Most often, soil is too acid, so it is treated with quicklime (calcium oxide), slaked lime (calcium hydroxide) or chalk (calcium carbonate). These are all bases and are quite cheap.

Slide 21 : 21

Slide 22 : When a metal reacts with an acid it gives off hydrogen (which can be “popped” using a lit splint). The other product is a salt. Calcium + hydrochloric acid Zinc + Nitric acid Iron + hydrochloric acid Lithium + Sulphuric acid ? Calcium Chloride + hydrogen ? Zinc Nitrate + hydrogen ? Iron Chloride + hydrogen ? Lithium Sulphate + hydrogen Reactions of Metals and Acids

Slide 23 : Magnesium oxide + hydrochloric acid Calcium oxide + hydrochloric acid Sodium oxide + sulphuric acid METAL OXIDES AND ACIDS ? Magnesium Chloride + Water ? Calcium Chloride + Water ? Sodium Sulphate + Water

Slide 24 : Acid rain damages trees and buildings and can harm wildlife. What causes it? Acid Rain

Slide 25 : 25 Salt Preparations using ACIDS Hydrated copper (II) sulphate Sodium Chloride

Slide 26 : 26 Using: Soluble Base + Acid ? Salt + Water NaOH(aq) + HCl(aq) ? NaCl(aq) + H2O(l) The exact amount of alkali required can be determined using an indicator, but this stains the solution. By noting the volume required, it can be repeated using the same volumes but without indicator A cold glass rod dipped in and out of the solution will indicate when it is saturated   The hot saturated solution is allowed to sit and cool slowly

Slide 27 : 27 Using: Insoluble Base + Acid ? Salt + Water MgO(s) + 2HNO3(aq) ? Mg(NO3)2(aq) + H2O(l) In this case it is better to have the magnesium oxide solid in excess rather than the acid. The excess solid can simply be filtered off and the filtrate can be treated as in the previous case.

Slide 28 : 28 Using: Insoluble Base + Acid ? Salt + Water CuO(s) + H2SO4(aq) ? CuSO4(aq) + H2O(l) In this case it is better to have the copper oxide solid in excess rather than the acid. The excess solid can simply be filtered off and the filtrate can be treated as in the first and second examples

Slide 29 : 29 Recall that salts can be prepared using precipitation reactions as well. AB(aq) + CD(aq) ? AD(s) + CB(aq)   AgNO3(aq) + NaCl(aq) ? AgCl(s) + NaNO3(aq)     CuSO4(aq) + 2NaOH(aq) ? Cu(OH)2(s) + Na2SO4(aq)     Pb(NO3)2 (aq) + Na2CO3 (aq) ? PbCO3(s) + 2NaNO3(aq)     FeSO4(aq) + 2NaOH(aq) ? Fe(OH)2(s) + Na2SO4(aq)

Slide 30 : 30 CuSO4(aq) + 2NaOH(aq) ? Cu(OH)2(s) + Na2SO4(aq)   Ionic equation: Cu2+(aq) + 2OH-(aq) = Cu(OH)2(s) Making copper hydroxide crystals by precipitation The residue is the product but it is wet with sodium sulphate Wash the residue with distilled water Dry the solid between filter papers Complete drying in a desiccator

2 The methods used to prepare salts depend on whether the required salt is soluble or insoluble. Zinc sulphate, for example, is soluble while barium sulphate is insoluble. : 2 The methods used to prepare salts depend on whether the required salt is soluble or insoluble. Zinc sulphate, for example, is soluble while barium sulphate is insoluble. 2002, Paper 1

a) (i) Describe in detail how you would prepare a pure dry sample of zinc sulphate crystals in the laboratory starting from solid zinc carbonate and dilute sulphuric acid. ________________________________ ________________________________ ________________________________ ________________________________ ____________________________ [10] : a) (i) Describe in detail how you would prepare a pure dry sample of zinc sulphate crystals in the laboratory starting from solid zinc carbonate and dilute sulphuric acid. ________________________________ ________________________________ ________________________________ ________________________________ ____________________________ [10]

a) (i) Describe in detail how you would prepare a pure dry sample of zinc sulphate crystals in the laboratory starting from solid zinc carbonate and dilute sulphuric acid. Place a volume of dilute sulphuric acid in a beaker [1]. Warm acid [1]. Add/react/mix [1] zinc carbonate with stirring [1] until o more solid dissolves/no more gas is given off [1]. Filter [1] the mixture into an evaporating basin/beaker/crystallising dish [1]. Heat [1] the solution to reduce the volume [1]. Allow to cool [1], filter [1] decant off the crystals, desiccator/low temperature oven [1]. Do not accept – heat to dryness. (Max [10]/[13]) : a) (i) Describe in detail how you would prepare a pure dry sample of zinc sulphate crystals in the laboratory starting from solid zinc carbonate and dilute sulphuric acid. Place a volume of dilute sulphuric acid in a beaker [1]. Warm acid [1]. Add/react/mix [1] zinc carbonate with stirring [1] until o more solid dissolves/no more gas is given off [1]. Filter [1] the mixture into an evaporating basin/beaker/crystallising dish [1]. Heat [1] the solution to reduce the volume [1]. Allow to cool [1], filter [1] decant off the crystals, desiccator/low temperature oven [1]. Do not accept – heat to dryness. (Max [10]/[13])

Give a balanced symbol equation for the preparation of zinc sulphate. ____________________________ [2](iii) Give the names of two other zinc compounds which could be used to make zinc sulphate crystals from sulphuric acid. ____________________________ [2] : Give a balanced symbol equation for the preparation of zinc sulphate. ____________________________ [2](iii) Give the names of two other zinc compounds which could be used to make zinc sulphate crystals from sulphuric acid. ____________________________ [2]

Give a balanced symbol equation for the preparation of zinc sulphate. ZnCO3 + H2SO4 ? ZnSO4 + H2O + CO2 [2](iii) Give the names of two other zinc compounds which could be used to make zinc sulphate crystals from sulphuric acid. Zinc Oxide [1] Zinc Hydroxide [1] : Give a balanced symbol equation for the preparation of zinc sulphate. ZnCO3 + H2SO4 ? ZnSO4 + H2O + CO2 [2](iii) Give the names of two other zinc compounds which could be used to make zinc sulphate crystals from sulphuric acid. Zinc Oxide [1] Zinc Hydroxide [1]

b) (i) Describe in detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and magnesium sulphate. ____________________________ ____________________________ ____________________________ ____________________________ _________________________ [5] : b) (i) Describe in detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and magnesium sulphate. ____________________________ ____________________________ ____________________________ ____________________________ _________________________ [5]

b) (i) Describe in detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and magnesium sulphate. Mix [1] the solutions of barium chloride and magnesium sulphate. A white [1] precipitate [1] formed. Filter [1] the mixture, rinse/wash with cold water [1] and dry in an oven [1]. Accept suitable drying method. (Max [5]/[6]) : b) (i) Describe in detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and magnesium sulphate. Mix [1] the solutions of barium chloride and magnesium sulphate. A white [1] precipitate [1] formed. Filter [1] the mixture, rinse/wash with cold water [1] and dry in an oven [1]. Accept suitable drying method. (Max [5]/[6])

(ii) Give a balanced symbol equation for the preparation of barium sulphate. ________________________ [2](iii) Give the names of two other compounds which could be used to make barium sulphate instead of barium chloride and magnesium sulphate. ________________________ [2] : (ii) Give a balanced symbol equation for the preparation of barium sulphate. ________________________ [2](iii) Give the names of two other compounds which could be used to make barium sulphate instead of barium chloride and magnesium sulphate. ________________________ [2]

(ii) Give a balanced symbol equation for the preparation of barium sulphate. BaCl2 + MgSO4 ? BaSO4 + MgCl2 Ba2+ + SO42- ? BaSO4 [2](iii) Give the names of two other compounds which could be used to make barium sulphate instead of barium chloride and magnesium sulphate. Barium nitrate [1] Any soluble sulphate [1] accept correct formula. : (ii) Give a balanced symbol equation for the preparation of barium sulphate. BaCl2 + MgSO4 ? BaSO4 + MgCl2 Ba2+ + SO42- ? BaSO4 [2](iii) Give the names of two other compounds which could be used to make barium sulphate instead of barium chloride and magnesium sulphate. Barium nitrate [1] Any soluble sulphate [1] accept correct formula.

2 In a fish and chip shop there are two bottles on the counter. One contains table salt, the other vinegar. The labels of these bottles are shown below. : 2 In a fish and chip shop there are two bottles on the counter. One contains table salt, the other vinegar. The labels of these bottles are shown below. Table Salt Ingredients Sodium chloride, Anti-caking agent (magnesium carbonate) Vinegar Ingredients Ethanoic acid solution 2004, Paper 2

a)(i) How would you find the pH of the vinegar? _______________________________ _______________________________ [2](ii) What would you expect the pH of the vinegar to be? _______________________________ [1] : a)(i) How would you find the pH of the vinegar? _______________________________ _______________________________ [2](ii) What would you expect the pH of the vinegar to be? _______________________________ [1]

Slide 42 : 42 Orange Green Blue-green

a)(i) How would you find the pH of the vinegar? Universal indicator paper/solution/pH paper [1] compare to colour [1] chart or use a digital/electronic pH meter [2](ii) What would you expect the pH of the vinegar to be? In range 3-5 [1] : a)(i) How would you find the pH of the vinegar? Universal indicator paper/solution/pH paper [1] compare to colour [1] chart or use a digital/electronic pH meter [2](ii) What would you expect the pH of the vinegar to be? In range 3-5 [1]

(iii) Suggest the name of a compound that will react with ethanoic acid to produce a salt and name the salt produced. Compound name: ________________ [1] Salt name: ______________________ [1] : (iii) Suggest the name of a compound that will react with ethanoic acid to produce a salt and name the salt produced. Compound name: ________________ [1] Salt name: ______________________ [1]

(iii) Suggest the name of a compound that will react with ethanoic acid to produce a salt and name the salt produced. Compound name: any carbonate / oxide / hydroxide / hydrogencarbonate [1] Salt name: metal ethanoate [1] : (iii) Suggest the name of a compound that will react with ethanoic acid to produce a salt and name the salt produced. Compound name: any carbonate / oxide / hydroxide / hydrogencarbonate [1] Salt name: metal ethanoate [1]

b) Sodium chloride, the main ingredient of table salt, can be prepared in the laboratory form sodium hydroxide solution and hydrochloric acid.(i) Describe in detail how you would prepare pure dry crystals of sodium chloride from sodium hydroxide solution and hydrochloric acid. ______________________________________ ______________________________________ ______________________________________ ____________________________________ [8] : b) Sodium chloride, the main ingredient of table salt, can be prepared in the laboratory form sodium hydroxide solution and hydrochloric acid.(i) Describe in detail how you would prepare pure dry crystals of sodium chloride from sodium hydroxide solution and hydrochloric acid. ______________________________________ ______________________________________ ______________________________________ ____________________________________ [8]

(i) Describe in detail how you would prepare pure dry crystals of sodium chloride from sodium hydroxide solution and hydrochloric acid. Place measured [1] volume (using a pipette) of acid/alkali in conical flask. Add named indicator [1] e.g. phenolphtalein, add alkali/acid [1] colour change of indicator [2] wrong way round [1] e.g. pink to colourless using burette [1] Either note volume used [1] repeate using same volumes [1] of acid and alkali but without indicator or add charcoal [1] heat [1] filter [1] [8] : (i) Describe in detail how you would prepare pure dry crystals of sodium chloride from sodium hydroxide solution and hydrochloric acid. Place measured [1] volume (using a pipette) of acid/alkali in conical flask. Add named indicator [1] e.g. phenolphtalein, add alkali/acid [1] colour change of indicator [2] wrong way round [1] e.g. pink to colourless using burette [1] Either note volume used [1] repeate using same volumes [1] of acid and alkali but without indicator or add charcoal [1] heat [1] filter [1] [8]

(ii) Write a balanced symbol equation for the preparation of sodium chloride from sodium hydroxide and hydrochloric acid. _______________________________ [2](iii) The reaction in (b)(ii) is a neutralisation reaction. Write an ionic equation for neutralisation including state symbols. _______________________________ [2] : (ii) Write a balanced symbol equation for the preparation of sodium chloride from sodium hydroxide and hydrochloric acid. _______________________________ [2](iii) The reaction in (b)(ii) is a neutralisation reaction. Write an ionic equation for neutralisation including state symbols. _______________________________ [2]

(ii) Write a balanced symbol equation for the preparation of sodium chloride from sodium hydroxide and hydrochloric acid. NaOH + HCl ? NaCl + H2O [2](iii) The reaction in (b)(ii) is a neutralisation reaction. Write an ionic equation for neutralisation including state symbols. H+(aq) + OH-(aq) ? H2O(1) [2] : (ii) Write a balanced symbol equation for the preparation of sodium chloride from sodium hydroxide and hydrochloric acid. NaOH + HCl ? NaCl + H2O [2](iii) The reaction in (b)(ii) is a neutralisation reaction. Write an ionic equation for neutralisation including state symbols. H+(aq) + OH-(aq) ? H2O(1) [2]

(iv) Apart from table salt, give one other use of sodium chloride. _______________________________ [1] : (iv) Apart from table salt, give one other use of sodium chloride. _______________________________ [1]

(iv) Apart from table salt, give one other use of sodium chloride. De-icing roads [1] : (iv) Apart from table salt, give one other use of sodium chloride. De-icing roads [1]

c) The anti-caking agent magnesium carbonate is added to table salt to make it run freely. When table salt is eaten the magnesium carbonate reacts with the dilute hydrochloric acid in the stomach.(i) Write a balanced symbol equation for the reaction between magnesium carbonate and hydrochloric acid. _______________________________ [3] : c) The anti-caking agent magnesium carbonate is added to table salt to make it run freely. When table salt is eaten the magnesium carbonate reacts with the dilute hydrochloric acid in the stomach.(i) Write a balanced symbol equation for the reaction between magnesium carbonate and hydrochloric acid. _______________________________ [3]

c) The anti-caking agent magnesium carbonate is added to table salt to make it run freely. When table salt is eaten the magnesium carbonate reacts with the dilute hydrochloric acid in the stomach.(i) Write a balanced symbol equation for the reaction between magnesium carbonate and hydrochloric acid. MgCO3 + 2HCl ? MgCl2 + H2O + CO2 [3] : c) The anti-caking agent magnesium carbonate is added to table salt to make it run freely. When table salt is eaten the magnesium carbonate reacts with the dilute hydrochloric acid in the stomach.(i) Write a balanced symbol equation for the reaction between magnesium carbonate and hydrochloric acid. MgCO3 + 2HCl ? MgCl2 + H2O + CO2 [3]

(ii) Some solid magnesium carbonate was added to some hydrochloric acid in a test tube. State two observations which could be made. _______________________________ _______________________________ [2] : (ii) Some solid magnesium carbonate was added to some hydrochloric acid in a test tube. State two observations which could be made. _______________________________ _______________________________ [2]

(ii) Some solid magnesium carbonate was added to some hydrochloric acid in a test tube. State two observations which could be made. Bubbles/effervescence [1] test tube gets warm [1] carbonate disappears [1] colourless solution forms [1] (max [2]) [2] : (ii) Some solid magnesium carbonate was added to some hydrochloric acid in a test tube. State two observations which could be made. Bubbles/effervescence [1] test tube gets warm [1] carbonate disappears [1] colourless solution forms [1] (max [2]) [2]

d) The chip shop vinegar often becomes contaminated with table salt. Describe how would test a sample of the vinegar to confirm the presence of sodium ions. State any observations made. _______________________________ _______________________________ _______________________________ [3] : d) The chip shop vinegar often becomes contaminated with table salt. Describe how would test a sample of the vinegar to confirm the presence of sodium ions. State any observations made. _______________________________ _______________________________ _______________________________ [3]

d) The chip shop vinegar often becomes contaminated with table salt. Describe how would test a sample of the vinegar to confirm the presence of sodium ions. State any observations made. Use piece of nichrome wire/flame test rod [1] dip in vinegar and place in flame [1] yellow [1] flame indicates sodium ions. [3] : d) The chip shop vinegar often becomes contaminated with table salt. Describe how would test a sample of the vinegar to confirm the presence of sodium ions. State any observations made. Use piece of nichrome wire/flame test rod [1] dip in vinegar and place in flame [1] yellow [1] flame indicates sodium ions. [3]

3 Indicators are substances that change colour when they are added to acids and alkalis.a) Complete the table below for the two indicators, methyl orange and phenolphthalein. : 3 Indicators are substances that change colour when they are added to acids and alkalis.a) Complete the table below for the two indicators, methyl orange and phenolphthalein. 2005, Paper 2

3 Indicators are substances that change colour when they are added to acids and alkalis.a) Complete the table below for the two indicators, methyl orange and phenolphthalein. : 3 Indicators are substances that change colour when they are added to acids and alkalis.a) Complete the table below for the two indicators, methyl orange and phenolphthalein.

b) The method used to prepare a salt depends on whether the salt is soluble or insoluble.(i) Barium sulphate is insoluble. Describe is detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and zinc sulphate _____________________________________ _____________________________________ _____________________________________ [5] Quality of communication [2] : b) The method used to prepare a salt depends on whether the salt is soluble or insoluble.(i) Barium sulphate is insoluble. Describe is detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and zinc sulphate _____________________________________ _____________________________________ _____________________________________ [5] Quality of communication [2]

b) The method used to prepare a salt depends on whether the salt is soluble or insoluble.(i) Barium sulphate is insoluble. Describe is detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and zinc sulphate Mix [1] solutions filter [1] residue [1] rinse with water [1] dry in an oven [5] Quality of communication [2] : b) The method used to prepare a salt depends on whether the salt is soluble or insoluble.(i) Barium sulphate is insoluble. Describe is detail how you would prepare a pure dry sample of barium sulphate in the laboratory starting with solutions of barium chloride and zinc sulphate Mix [1] solutions filter [1] residue [1] rinse with water [1] dry in an oven [5] Quality of communication [2]

(ii) Write a balanced ionic equation to show the formation of barium sulphate. ______________________________ [2] : (ii) Write a balanced ionic equation to show the formation of barium sulphate. ______________________________ [2]

(ii) Write a balanced ionic equation to show the formation of barium sulphate. Ba2+ + SO2-4 ? BaSO4 [2] : (ii) Write a balanced ionic equation to show the formation of barium sulphate. Ba2+ + SO2-4 ? BaSO4 [2]

c) Copper(II) sulphate is a soluble salt. It may be prepared by adding an excess of copper(II) oxide to dilute sulphuric acid and warming. The mixture is then filtered. The filtrate is then partly evaporated and allowed to stand until crystals form. The crystals are filtered off and dried. : c) Copper(II) sulphate is a soluble salt. It may be prepared by adding an excess of copper(II) oxide to dilute sulphuric acid and warming. The mixture is then filtered. The filtrate is then partly evaporated and allowed to stand until crystals form. The crystals are filtered off and dried.

(i) Why is an excess of copper(II) oxide used? _______________________________ _______________________________ [2](ii) Why is the filtrate not evaporated to dryness? _______________________________ _______________________________ [2] : (i) Why is an excess of copper(II) oxide used? _______________________________ _______________________________ [2](ii) Why is the filtrate not evaporated to dryness? _______________________________ _______________________________ [2]

(i) Why is an excess of copper(II) oxide used? All acid [1] has reacted [1] [2](ii) Why is the filtrate not evaporated to dryness? Water of crystallisation [1] removed [1] or no crystal [1] formation [1] [2] : (i) Why is an excess of copper(II) oxide used? All acid [1] has reacted [1] [2](ii) Why is the filtrate not evaporated to dryness? Water of crystallisation [1] removed [1] or no crystal [1] formation [1] [2]

(iii) How are the crystals dried? _______________________________ _______________________________ [1](iv) Why is copper metal not used with sulphuric acid to prepare copper(II) sulphate? _______________________________ _______________________________ [1] : (iii) How are the crystals dried? _______________________________ _______________________________ [1](iv) Why is copper metal not used with sulphuric acid to prepare copper(II) sulphate? _______________________________ _______________________________ [1]

(iii) How are the crystals dried? Between filter papers/low temperature oven/desiccator [1](iv) Why is copper metal not used with sulphuric acid to prepare copper(II) sulphate? No reaction [1] : (iii) How are the crystals dried? Between filter papers/low temperature oven/desiccator [1](iv) Why is copper metal not used with sulphuric acid to prepare copper(II) sulphate? No reaction [1]

4a) hydrochloric acid reacts with zinc hydroxide and potassium hydroxide. These reactions produce salts. Zinc hydroxide is a base. Potassium hydroxide is an alkali.(i) Name one other base. _______________________________ [1](ii) What is meant by the term alkali? _______________________________ [2] : 4a) hydrochloric acid reacts with zinc hydroxide and potassium hydroxide. These reactions produce salts. Zinc hydroxide is a base. Potassium hydroxide is an alkali.(i) Name one other base. _______________________________ [1](ii) What is meant by the term alkali? _______________________________ [2] 2006, Paper 1

4a) hydrochloric acid reacts with zinc hydroxide and potassium hydroxide. These reactions produce salts. Zinc hydroxide is a base. Potassium hydroxide is an alkali.(i) Name one other base. Any other metal oxide or hydroxide. Not zinc hydroxide / potassium hydroxide. [1](ii) What is meant by the term alkali? Soluble [1] base [1] [2] : 4a) hydrochloric acid reacts with zinc hydroxide and potassium hydroxide. These reactions produce salts. Zinc hydroxide is a base. Potassium hydroxide is an alkali.(i) Name one other base. Any other metal oxide or hydroxide. Not zinc hydroxide / potassium hydroxide. [1](ii) What is meant by the term alkali? Soluble [1] base [1] [2]

b) Zinc hydroxide acts as a base with hydrochloric acid. However, it also reacts with alkalis like potassium hydroxide.(i) What term is used for substances like zinc hydroxide which react with both acids and alkalis? _______________________________ [1](ii) Name one other metal hydroxide which behaves in this way. _______________________________ [1] : b) Zinc hydroxide acts as a base with hydrochloric acid. However, it also reacts with alkalis like potassium hydroxide.(i) What term is used for substances like zinc hydroxide which react with both acids and alkalis? _______________________________ [1](ii) Name one other metal hydroxide which behaves in this way. _______________________________ [1]

b) Zinc hydroxide acts as a base with hydrochloric acid. However, it also reacts with alkalis like potassium hydroxide.(i) What term is used for substances like zinc hydroxide which react with both acids and alkalis? Amphoteric [1](ii) Name one other metal hydroxide which behaves in this way. Aluminium hydroxide [1] : b) Zinc hydroxide acts as a base with hydrochloric acid. However, it also reacts with alkalis like potassium hydroxide.(i) What term is used for substances like zinc hydroxide which react with both acids and alkalis? Amphoteric [1](ii) Name one other metal hydroxide which behaves in this way. Aluminium hydroxide [1]

(iii) Write balanced symbol equations for the reactions between: (1) zinc hydroxide and hydrochloric acid _______________________________ [1] (2) zinc hydroxide and potassium hydroxide _______________________________ [1] : (iii) Write balanced symbol equations for the reactions between: (1) zinc hydroxide and hydrochloric acid _______________________________ [1] (2) zinc hydroxide and potassium hydroxide _______________________________ [1]

(iii) Write balanced symbol equations for the reactions between: (1) zinc hydroxide and hydrochloric acid Zn(OH)2 + 2HCl ? ZnCl2 + 2H2O[1](2) zinc hydroxide and potassium hydroxide Zn(OH)2 + 2KOH ? K2ZnO2 + 2H2O [1] or Zn(OH)2 + 2KOH ? K2Zn(OH)4 [1] : (iii) Write balanced symbol equations for the reactions between: (1) zinc hydroxide and hydrochloric acid Zn(OH)2 + 2HCl ? ZnCl2 + 2H2O[1](2) zinc hydroxide and potassium hydroxide Zn(OH)2 + 2KOH ? K2ZnO2 + 2H2O [1] or Zn(OH)2 + 2KOH ? K2Zn(OH)4 [1]

Slide 75 : c) The reaction between zinc carbonate and hydrochloric acid produces the salt zinc chloride. The diagram below details how pure, dry crystals of zinc chloride may be produced.

(i) What piece of apparatus would you use to measure 23cm3 of hydrochloric acid? _______________________________ [1](ii) Explain why the zinc carbonate is added until it is in excess. _______________________________ _______________________________ [1] : (i) What piece of apparatus would you use to measure 23cm3 of hydrochloric acid? _______________________________ [1](ii) Explain why the zinc carbonate is added until it is in excess. _______________________________ _______________________________ [1]

(i) What piece of apparatus would you use to measure 23cm3 of hydrochloric acid? Measuring cylinder / pipette / burette [1](ii) Explain why the zinc carbonate is added until it is in excess. Ensure all acid reacted [1] : (i) What piece of apparatus would you use to measure 23cm3 of hydrochloric acid? Measuring cylinder / pipette / burette [1](ii) Explain why the zinc carbonate is added until it is in excess. Ensure all acid reacted [1]

(iii) Give one way in which you would know the zinc carbonate is in excess. _______________________________ _______________________________ [1](iv) What is the general name given to the solid trapped by the filter paper? _______________________________ [1] : (iii) Give one way in which you would know the zinc carbonate is in excess. _______________________________ _______________________________ [1](iv) What is the general name given to the solid trapped by the filter paper? _______________________________ [1]

(iii) Give one way in which you would know the zinc carbonate is in excess. Solid remaining / no more gas evolved [1](iv) What is the general name given to the solid trapped by the filter paper? Residue [1] : (iii) Give one way in which you would know the zinc carbonate is in excess. Solid remaining / no more gas evolved [1](iv) What is the general name given to the solid trapped by the filter paper? Residue [1]

(v) What is the general name given to the filtered solution? _______________________________ [1](vi) Explain why crystals form as the solution is cooled. _______________________________ _______________________________ [2] : (v) What is the general name given to the filtered solution? _______________________________ [1](vi) Explain why crystals form as the solution is cooled. _______________________________ _______________________________ [2]

(v) What is the general name given to the filtered solution? Filtrate [1](vi) Explain why crystals form as the solution is cooled. Solubility [1] decreases [1] on cooling or More solute [1] than solution can hold [1] : (v) What is the general name given to the filtered solution? Filtrate [1](vi) Explain why crystals form as the solution is cooled. Solubility [1] decreases [1] on cooling or More solute [1] than solution can hold [1]

(vii) Give two methods of drying the crystals. 1. _____________________________ [1] 2. _____________________________ [1] : (vii) Give two methods of drying the crystals. 1. _____________________________ [1] 2. _____________________________ [1]

(vii) Give two methods of drying the crystals. Between two pieces of filter paper / desiccator / low temperature oven. Any two [2] : (vii) Give two methods of drying the crystals. Between two pieces of filter paper / desiccator / low temperature oven. Any two [2]

d) Zinc chloride consists of zinc ions and chloride ions. The table below describes a chemical test for zinc ions. : d) Zinc chloride consists of zinc ions and chloride ions. The table below describes a chemical test for zinc ions.

d) Zinc chloride consists of zinc ions and chloride ions. The table below describes a chemical test for zinc ions. : d) Zinc chloride consists of zinc ions and chloride ions. The table below describes a chemical test for zinc ions.

(i) Complete the table giving the observations for the test for zinc ions. [2](ii) Write a balanced ionic equation for the reaction between the zinc ions in zinc chloride and hydroxide ions in sodium hydroxide. _______________________________ [3] : (i) Complete the table giving the observations for the test for zinc ions. [2](ii) Write a balanced ionic equation for the reaction between the zinc ions in zinc chloride and hydroxide ions in sodium hydroxide. _______________________________ [3]

(i) Complete the table giving the observations for the test for zinc ions. White [1] precipitate [1] [2](ii) Write a balanced ionic equation for the reaction between the zinc ions in zinc chloride and hydroxide ions in sodium hydroxide. Zn2+ + 2OH- ? Zn(OH)2 [3] [1] [1] + [1] for balancing : (i) Complete the table giving the observations for the test for zinc ions. White [1] precipitate [1] [2](ii) Write a balanced ionic equation for the reaction between the zinc ions in zinc chloride and hydroxide ions in sodium hydroxide. Zn2+ + 2OH- ? Zn(OH)2 [3] [1] [1] + [1] for balancing

Slide 88 : 88

Slide 89 : 89 Thanks for viewing. Do consider using others in this Series. Atomic Structure and Bonding. Inorganic: Metal Chemistry Inorganic: Non-metal Chemistry Redox and Electrolytic Chemistry Organic Chemistry Calculations in Chemistry Hard Water Acids Bases & Salt Preparations Kinetics and Energetics Miscellaneous Also, check back on this video-lesson from time-to-time during the duration of your course. F Scullion