Acids, Bases, Salts Specification points Year 0/Year, Acids, Bases, Salts recaps year 9 work on this topic Reactions of acids know how to write and predict the products when given reactants for the following types of equations and use the formulae of common ions to write balanced equations Metal and acids produce salts and hydrogen and these are redox reactions which you can explain in terms of gain or loss of electrons. Metal carbonates and acids produce salt and water and carbon dioxide Hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates Students should be able to: predict products from given reactants use the formulae of common ions to deduce the formulae of salts. Soluble salts Soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates. Be able to describe how to make a pure, dry sample of a soluble salt from an insoluble oxide or carbonate (base). Key steps are the solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt. Salt solutions can be crystallised to produce solid salts. The ph scale and neutralisation The ph scale, from 0 to 4, is a measure of the acidity or alkalinity of a solution, measured using universal indicator or a ph probe. A solution with ph 7 is neutral. Aqueous solutions of alkalis contain hydroxide ions (OH ). Acids produce hydrogen ions (H + ) in aqueous solutions. In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water. How to describe the use of universal indicator to measure the approximate ph of a solution and use the ph scale to identify acidic or alkaline solutions. Strong and weak acids A strong acid is completely ionised in solution eg: hydrochloric, nitric and sulfuric acids. A weak acid is only partially ionised in solution eg ethanoic, citric and carbonic acids. For a given concentration of aqueous solutions, the stronger an acid, the lower the ph. As the ph decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 0. How to use and explain the terms dilute and concentrated (in terms of amount of substance), and weak and strong (in terms of the degree of ionisation) in relation to acids describe neutrality and relative acidity in terms of the effect on hydrogen ion concentration and the numerical value of ph (whole numbers only). Identification of common gases Test for hydrogen - The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound. Test for oxygen - The test for oxygen uses a glowing splint inserted into a test tube of the gas. The splint relights in oxygen. Test for carbon dioxide - The test for carbon dioxide uses an aqueous solution of calcium
hydroxide (lime water). When carbon dioxide is shaken with or bubbled through limewater the limewater turns milky (cloudy). Test for chlorine - The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white. Independent Study suggestions Look at the specification points above use the textbook pages (48-63) Watch the Fuse School short 3-4 minute explanation videos on any areas you need a little more help with: ph scale: https://www.fuseschool.org/topics/63/contents/08 What makes something an alkali: https://www.fuseschool.org/topics/63/contents/296 Strong and weak alkalis: https://www.fuseschool.org/topics/63/contents/376 What makes something acidic: https://www.fuseschool.org/topics/63/contents/937 Indicators: https://www.fuseschool.org/topics/63/contents/879 Theory of acids and bases: https://www.fuseschool.org/topics/63/contents/294 Strong and weak acids: https://www.fuseschool.org/topics/63/contents/062 Conjugate acids and bases: https://www.fuseschool.org/topics/63/contents/293 Other acids: https://www.fuseschool.org/topics/63/contents/403 Metal and acid reactions: https://www.fuseschool.org/topics/63/contents/820 What are salts: https://www.fuseschool.org/topics/63/contents/823 Titrations: https://www.fuseschool.org/topics/63/contents/05 Titration calculations: https://www.fuseschool.org/topics/63/contents/06 Neutralisation of alkalis: https://www.fuseschool.org/topics/63/contents/822 Ammonium salts: https://www.fuseschool.org/topics/63/contents/82 Making soluble salts: https://www.fuseschool.org/topics/63/contents/940 Solubility rules for salts: https://www.fuseschool.org/topics/63/contents/824 Making insoluble salts: https://www.fuseschool.org/topics/63/contents/939 Collecting gases https://www.fuseschool.org/topics/62 Testing for different gases https://www.fuseschool.org/topics/62/contents/28 Now have a go at answering the questions below and then mark them with the markscheme.
Q. Here is a word equation for a chemical reaction. copper oxide + sulphuric acid copper sulphate + water Write down everything that the word equation tells you about the reaction.... (Total 4 marks) Q2. Use the Formulae of Some Common Ions table on the Data Sheet to help you to answer this question. Acids react with alkalis to form salts and water. Complete the table below by writing in the name and formula of the salt formed in each reaction. The first one has been done for you. Acid Alkali Salt Formula of salt Hydrochloric acid Sodium hydroxide Sodium chloride NaCl Nitric acid Sulphuric acid Sodium hydroxide Potassium hydroxide (Total 4 marks) Q3. Sodium carbonate reacts with acids. (i) Complete the word equation. sodium carbonate + hydrochloric acid sodium chloride +... + water () Name the salt produced if sodium carbonate reacts with dilute nitric acid... () Q4. (i) Which acid from the list should the student add to sodium hydroxide solution to make sodium sulphate? ethanoic acid hydrochloric acid nitric acid sulphuric acid.. () When the acid was added to the alkali the beaker became warm. Name the type of reaction that releases heat.. () (iii) Use the Data Sheet to help you to write the formula of sodium sulphate. Formula:... ()
Q5. The table shows some information about acids and alkalis. Name of acid or alkali Type Ions produced in solution ph Effect on Universal Indicator Hydrochloric acid Strong acid H + Cl Goes red Sodium hydroxide Strong alkali Na + OH 3 Goes purple Use the information in the table to help you answer parts (a) and (b).. (a) Draw a ring around the correct answer to complete each sentence. (i) Hydrochloric acid is acidic. Cl - This is because it contains H + ions OH - () Sodium hydroxide solution is alkaline. H + This is because it contains Na + ions OH - higher than () (iii) The ph of acids is lower than the ph of alkalis. the same as () (b) Ethanoic acid is a weak acid. Universal Indicator can be used to show that hydrochloric acid is a stronger acid than ethanoic acid of the same concentration. Explain how......... (2)
(c) Draw a ring around the correct answer to complete this sentence. completely Strong acids and strong alkalis are not ionised in water. partially () (d) The diagram shows the apparatus used to find the volume of hydrochloric acid that reacts with 25.0 cm 3 of sodium hydroxide solution. (i) Which one of the following is the correct name for A? Draw a ring around your answer. beaker conical flask pipette () Use the correct word from the box to complete the sentence. distillation filtration titration The method used to find the volume of acid that reacts with a known volume of alkali is... () (iii) Suggest one way to make the results more reliable.... () (Total 9 marks)
Q6. The diagrams show what happens when an acid is added to an alkali. (a) What is present in the flask at stage 2, besides universal indicator and water?.. (). (b) ions. Write an ionic equation to show how water is formed in this reaction and state the sources of the.... (3) (Total 4 marks) Q7. Ammonium nitrate and potassium chloride are both salts. They can be made by neutralisation reactions. salts. Choose substances from the box to complete the word equations for the formation of these two ammonia hydrochloric acid nitric acid potassium nitrate water potassium hydroxide ammonia +... ammonium nitrate + water... + hydrochloric acid potassium chloride +... (Total 3 marks)
Q8. The salt sodium hydrogen phosphate (Na 2 HPO 4 ) is used as a softening agent in processed cheese. It can be made by reacting phosphoric acid (H 3 PO 4 ) with an alkali. (a) Complete the name of an alkali that could react with phosphoric acid to make sodium hydrogen phosphate.... hydroxide () (b) What is the name given to a reaction in which an acid reacts with an alkali to make a salt?... () (c) How would the ph change when alkali is added to the phosphoric acid solution?...... () (d) What ions are present when any acid is dissolved in water?... () (e) What ions are present when any alkali is dissolved in water?... (). (f) Write a chemical equation for the reaction which takes place between the ions you have named in (e) and (f).... (). Q9. (a) Citric acid produces hydrogen ions in aqueous solution. These ions can be represented as H + (aq). Complete this sentence. The (aq) means that the acid has been dissolved in.... ()
(b) The diagram represents a hydrogen atom, H. Use the diagram to explain why a hydrogen ion, H +, is a proton....... () (c) Citric acid is a weak acid. Draw a ring around the correct answer to complete the sentence. has a low boiling point. The word weak means that the acid is dilute. is partially ionised in water. (). (d) A student measured the ph of four acids, A, B, C and D. The acids were the same concentration. The same quantity of magnesium ribbon was added to each of the acids. The volume of gas produced after 5 minutes was recorded. The results are shown in the table. Acid ph Volume of gas in cm 3 A 2 8 B 5 6 C 24 D 4 2 (i) State one way in which the student made sure that the experiment was fair. ()
Use the results to arrange the acids, A, B, C and D in order of decreasing acid strength. Most acidic... Least acidic. (). (e) When acids react with alkalis, the hydrogen ions from the acid react with the hydroxide ions from the alkali. (i) Which one of the following represents the formula of a hydroxide ion? Draw a ring around your answer. H O OH () Draw a ring around the correct answer to complete the sentence. acidic. A solution with more hydrogen ions than hydroxide ions is alkaline. neutral. Q0.A student investigated the reactions of copper carbonate and copper oxide with dilute hydrochloric acid. In both reactions one of the products is copper chloride. (a) Describe how a sample of copper chloride crystals could be made from copper carbonate and dilute hydrochloric acid. () (Total 7 marks)....... (4) (b) A student wanted to make.0 g of copper chloride. The equation for the reaction is: CuCO 3 + 2HCl CuCl 2 + H 2 O + CO 2 Relative atomic masses, A r : H = ; C = 2; O = 6; Cl = 35.5; Cu = 63.5
Calculate the mass of copper carbonate the student should react with dilute hydrochloric acid to make.0 g of copper chloride. Mass of copper carbonate =... g (4) (c) The percentage yield of copper chloride was 79. %. Calculate the mass of copper chloride the student actually produced. Actual mass of copper chloride produced =... g (2) (d) Look at the equations for the two reactions: Reaction Reaction 2 CuCO 3 (s) + 2HCl(aq) CuCl 2 (aq) + H 2 O(l) + CO 2 (g) CuO(s) + 2HCl(aq) CuCl 2 (aq) + H 2 O(l) Reactive formula masses: CuO = 79.5; HCl = 36.5; CuCl 2 = 34.5; H 2 O = 8 The percentage atom economy for a reaction is calculated using: Calculate the percentage atom economy for Reaction 2. Percentage atom economy =... % (3) (e) The atom economy for Reaction is 68.45 %. Compare the atom economies of the two reactions for making copper chloride. Give a reason for the difference. ()
Q. (a) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. The salt called potassium chloride is made when potassium hydroxide solution reacts with hydrochloric acid. potassium hydroxide solution + hydrochloric acid potassium chloride solution + water Describe a method for making crystals of potassium chloride from potassium hydroxide solution and hydrochloric acid. In this method you should: describe how you will add the correct amount of the hydrochloric acid to neutralise the potassium hydroxide solution describe how you will get crystals of potassium chloride. (6)
(b) Ammonium nitrate is another salt. Ammonium nitrate is made when ammonia solution is neutralised with an acid. Name the acid to complete the word equation. ammonia +... acid ammonium nitrate () (c) Read the information. Ammonium nitrate good or bad? Some farmers put a lot of ammonium nitrate on their farmland. Many people are worried about this use of ammonium nitrate. Rain water can wash the ammonium nitrate off the farmland and into rivers and lakes. The ammonium nitrate may get into drinking water supplies and could be harmful to health. (i) Why do some farmers put ammonium nitrate on their farmland?.... () Tick ( Which one of the questions in the table cannot be answered by science alone? ) one question. Question Tick ( ) How much ammonium nitrate is in drinking water? Should farmers stop using ammonium nitrate on their farmland? Is ammonium nitrate soluble in rain water? Give two reasons why this question cannot be answered by science alone......... (3) (Total marks)
Q2.Limestone is used as a building material. Acid rain erodes limestone. (a) Limestone contains calcium carbonate. The symbol equation for the reaction of calcium carbonate with hydrochloric acid is shown. CaCO 3 (s) + 2HCl(aq) CaCl 2 (aq) + H 2 O(l) + CO 2 (g) Describe a test to show that carbon dioxide is produced in this reaction. Give the result of the test......... (2) (b) Gases from vehicle exhausts produce sulfuric acid and nitric acid. A student investigated the reaction of these two acids with calcium carbonate (limestone). The type of acid was changed but all other variables were kept the same. The student measured the volume of carbon dioxide produced each minute for a total of 0 minutes. He did this first for the reaction between dilute sulfuric acid and a cube of calcium carbonate (limestone). The student repeated the experiment using dilute nitric acid in place of the dilute sulfuric acid. The results are shown below. (i) State two variables that must be kept the same for this investigation....... (2)
(i) Reacting calcium carbonate with sulfuric acid gave different results to nitric acid. The symbol equations for the reaction of calcium carbonate with sulfuric acid and with nitric acid are shown below. CaCO 3 (s) + H 2 SO 4 (aq) CaSO 4 (s) + H 2 O(l) + CO 2 (g) CaCO 3 (s) + 2HNO 3 (aq) Ca(NO 3 ) 2 (aq) + H 2 O(l) + CO 2 (g) Describe how the results for sulfuric acid are different and use the symbol equations to explain this difference................. (3) (Total 7 marks) Q3.Calcium chloride (CaCl 2 ) is a soluble salt. Calcium chloride can be made by reacting dilute hydrochloric acid with either solid calcium oxide or solid calcium carbonate. (a) Name the type of reaction that takes place when dilute hydrochloric acid reacts with calcium oxide.. () (b) Write a balanced symbol equation for the reaction of dilute hydrochloric acid with calcium oxide.. (2) (c) A student added solid calcium oxide to dilute hydrochloric acid in a beaker. The student added solid calcium carbonate to dilute hydrochloric acid in another beaker. Describe one difference between the two reactions that the student would see. ()
(d) Describe how crystals of calcium chloride can be made from calcium carbonate and dilute hydrochloric acid. (4) (e) A student dissolved some crystals of a salt in water. The student added sodium hydroxide solution to the salt solution. The student added sodium hydroxide solution until it was in excess. (i) Describe what the student would see if the salt contained calcium ions. (2) ions? Why does the result you have described in part (e)(i) not prove that the salt contains calcium () (iii) Describe an additional test the student could do that would prove the salt contains calcium ions. (2) (Total 3 marks)
Answers: M. correct use of react/reaction/reactants NOT mixed added to join/combine/displace NOT equals correct use of produce/products/gives/forms/makes/creates reactants correctly identified products correctly identified (copper oxide reacts with sulphuric acid to produce copper sulphate and water, will be awarded all 4 marks) for mark each Reactants must be correctly identified for react mark to be given. Similarly for products [4] M2. sodium nitrate N ano 3 do not credit lower case N or O, upper case A potassium sulphate K 2SO 4 accept potassium hydrogen sulphate or KHSO 4 do not credit lower case K, S or O ignore charges on ions [4] M3. (i) carbon dioxide (allow CO 2) for mark sodium nitrate (accept correct formula) for mark [2] M4. (i) sulphuric acid / H 2SO 4 accept sulfuric for one mark exothermic for one mark (iii) Na 2SO 4 / (Na) 2SO 4 / Na 2(SO 4) / (Na + ) 2SO 4 2 for one mark lower case O(Na 2SO 4) not accepted / tops of subscripted letters should be in line or lower than lower case letters of symbols
[3] M5. (a) (i) H + OH (iii) lower than (b) with HCl: UI goes red / pink allow a comparison eg redder than ethanoic acid has a ph 0,,2 or 3 allow a comparison eg has ph less than ethanoic acid. do not accept an incorrect ph. or with ethanoic acid: UI goes orange / yellow () allow a comparison with HCl (c) has a ph 4 / or above (but less than 7) () allow a comparison with HCl completely (d) (i) conical flask (iii) titration repeat allow compare with another students results or take average [9] (a) (b) sodium ions and chloride ions (not chlorine) allow sodium chloride/salt/common salt for mark H + + OH H 2O H + from (hydrochloric) acid OH - from alkali/sodium hydroxide lose mark if no charge shown disregard other ions each for mark
3 [4] M7. nitric acid potassium hydroxide water M8. (a) sodium [3] (b) neutralisation (c) increase/inc. number (d) H + (e) OH (f) H + + OH H 2O [6] M9. (a) water / H 2O / hydrogen oxide (b) eg H (atom) loses an electron to form H + or only a proton left (c) is partially ionised in water (d) (i) eg same concentration / quantity of Mg accept: volume of acid / ribbon for both / same time accept: volume of gas measured under the same conditions C A D B (e) (i) OH acidic [7]
M0.(a) add excess copper carbonate (to dilute hydrochloric acid) accept alternatives to excess, such as until no more reacts filter (to remove excess copper carbonate) reject heat until dry heat filtrate to evaporate some water or heat to point of crystallisation accept leave to evaporate or leave in evaporating basin leave to cool (so crystals form) until crystals form must be in correct order to gain 4 marks (b) M r CuCl 2 = 34.5 correct answer scores 4 marks moles copper chloride = (mass / M r = / 34.5) = 0.087843866 M r CuCO 3 = 23.5 Mass CuCO 3 (=moles M 2 = 0.0878 23.5) = 0.(00) accept 0. with no working shown for 4 marks (c) or.0 0.79 8.70 (g) accept 8.70(g) with no working shown for 2 marks (d) Total mass of reactants = 52.5 34.5 52.5 allow ecf from step 88.20 (%) allow 88.20 with no working shown for 3 marks (e) atom economy using carbonate lower because an additional product is made or carbon dioxide is made as well allow ecf [4]
M. (a) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response.examiners should also apply a best-fit approach to the marking. 0 marks No relevant content. Level (-2 marks) There is a simple description of a laboratory procedure for obtaining potassium chloride. Level 2 (3-4 marks) There is a clear description of a laboratory procedure for obtaining potassium chloride from potassium hydroxide solution and hydrochloric acid that does not necessarily allow the procedure to be completed successfully by another person. The answer must include the use of an indicator or a method of obtaining crystals. Level 3 (5-6 marks) There is a detailed description of a laboratory procedure for obtaining potassium chloride from potassium hydroxide solution and hydrochloric acid that can be followed by another person. The answer must include the use of an indicator and a method of obtaining crystals. examples of the chemistry/social points made in the response: One reagent in beaker (or similar) Add (any named) indicator Add other reagent Swirl or mix Add dropwise near end point Stop addition at change of indicator colour Note volume of reagent added Repeat without indicator, adding same volume of reagent or remove indicator using charcoal Pour solution into basin / dish Heat (using Bunsen burner) Leave to crystallise / leave for water to evaporate / boil off water Accept any answers based on titration 6 (b) nitric (acid) allow HNO 3 ignore incorrect formula (c) (i) because it is a fertiliser / helps plants grow allow plant food do not accept pesticide / herbicide / neutralising soil tick by: Should farmers stop using ammonium nitrate on their land?
any two from: cannot be done by experiment accept difficult to get / not enough evidence based on opinion / view allow must be done by survey ethical or economic issue if top box ticked allow mark for drinking water varies from place to place 2 [] [8] M2. (a) limewater or calcium hydroxide solution (reacts with carbon dioxide and) turns cloudy / milky linked to first point if no other mark awarded puts out lighted splint gains mark (b) (i) any two from: same volume / amount of the acids concentration of the acids temperature same surface area / size / mass / amount of calcium carbonate same measuring equipment 2 any three from: (after about 4 minutes) the sulfuric acid stops reacting or nitric acid continues to react accept more CO 2 with nitric acid at any time after 4 minutes (initially) the reaction with sulfuric acid is faster (the reaction stops) because calcium sulfate is a solid allow sulfuric acid produces a solid (the reaction continues) because calcium nitrate is soluble / in solution / aqueous allow nitric acid produces an (aqueous) solution because the calcium sulfate prevents the sulfuric acid reacting with the calcium carbonate (the rate is faster) because sulfuric acid contains two hydrogens 3 [7]
M3.(a) neutralisation ignore reference to exothermic or endothermic (b) 2 HCl + CaO CaCl 2 + H 2O accept multiples and fractions formulae ignore state symbols balancing (dependent on first mark) (c) (the carbonate has) fizzing / bubbles / effervescence ignore dissolving ignore gas produced (d) add excess calcium carbonate to acid (and stir) / add CaCO 3 until fizzing stops ignore heating the acid accept answer using calcium oxide in place of calcium carbonate (remove excess calcium carbonate by) filter(ing) warm until a saturated solution forms / point of crystallisation / crystals start to form do not accept heat until all water gone leave to cool dependent on previous mark If solution not heated allow leave to evaporate () until crystals form () (e) (i) white precipitate / solid (forms) insoluble in excess or remains or no (further) change in excess dependent on a precipitate / solid forming same result with magnesium (ions) do not accept reference to any other ion(s) that do not give a white precipitate accept other named ions that do give a white precipitate (iii) flame test or description of flame test gives a red flame accept brick red or orange-red or scarlet do not accept crimson [3] [7]