CAIE Chemistry (9701)

Acids donate protons, H , in aqueous solution. The number of moles of H donated per mole of acid is the proticity of the acid. In this experiment, you will carry out a titration to determine the proticity of phosphoric acid, H , when it reacts with sodium hydroxide, NaOH. sodium hydroxide, NaOH. FA 3 is thymolphthalein indicator.

Method of FA 1 into a conical flask. The rough titre is cm in each accurate titration.

From your accurate titration results, calculate a suitable mean value to use in your calculations. Show clearly how you obtained the mean value. of FA 1 required cm of FA 2. [1]IIIVII

Calculations

Calculate the amount, in mol, of sodium hydroxide present in the volume of FA 2 calculated in

. amount of NaOH = mol

Use the information on page 2 to calculate the amount, in mol, of phosphoric acid present of FA 1. amount of H = mol

Deduce whether phosphoric acid behaves as a monoprotic, diprotic or triprotic acid in this titration. Explain your reasoning. is a protic acid. explanation

Give the equation for this reaction of phosphoric acid, H , with sodium hydroxide. to measure FA 1. Calculate the maximum percentage error in the volume of FA 1. Show your working. maximum percentage error = %

The student suggests it would be more accurate to measure the volume of FA 1 with a burette instead of the pipette. State whether you agree with the student. Explain your answer. [Total: 14]

In this experiment you will identify the metal, M, in a metal carbonate, MCO , by thermal decomposition.MCO

FA 4 is the metal carbonate, MCO

Method During the cooling period, you may wish to begin work on Question 3. Record the mass. Record the mass. Keep FA 5 for use in 2

. Results

Calculations

Calculate the amount, in mol, of carbon dioxide given off in your experiment. amount of CO = mol [1]III

Calculate the relative formula mass, M , of MCO of MCO =

From your results, deduce the identity of M. Show your reasoning. M is =

A student carries out the same procedure, using the same mass of solid. However, the student uses the basic carbonate, MCO , instead of the pure carbonate, MCO When the metal hydroxide part of the basic carbonate decomposes, metal oxide and steam are produced. The metal carbonate part decomposes in the usual way. State how the loss of mass from the student's solid compares with the loss of mass you obtained when you carried out your experiment. Explain your reasoning.

Use a spatula to transfer a small quantity of your cold residue, FA 5, into a test-tube. Record what you observe. State whether or not the thermal decomposition of MCO is complete. Justify your answer based on your observations. [2] [Total: 12] Qualitative analysis For each test you should record all your observations in the spaces provided. Examples of observations include: added You should record clearly at what stage in a test an observation is made. Where no change is observed you should write 'no change'. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. If any solution is warmed, a boiling tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests should be attempted.

Solutions FA 6 and FA 7 each contain one cation and one anion. All the ions are listed in the Qualitative analysis notes. Complete the table below. Table 3.1 test observations FA 6 FA 7 Test 1 Add an equal volume of aqueous potassium iodide, then add excess aqueous sodium thiosulfate. Test 2 Add a small spatula measure of zinc powder. Leave the mixture to stand. Test 3 Add a few drops of aqueous silver nitrate. Test 4 Add aqueous sodium hydroxide.

Construct an ionic equation for one of the reactions taking place in Test 2. Include state symbols.

FA 8 contains one anion and one cation. One of these ions contains nitrogen. Both ions are listed in the Qualitative analysis notes. Heat the test-tube gently at the start, then strongly until no further change occurs. Leave the test-tube to cool. Record all your observations.

Carry out further tests to identify each ion in FA 8. Record, in a table in the space below, the reagents, conditions and observations for the tests that positively identify each ion. You may wish to use the following page for rough working. Deduce the chemical formula of FA 8. You must use a boiling tube if any liquid is heated. The formula of FA 8 is . [6] [Total: 14] Use this page for any rough working. Qualitative analysis notes 1 Reactions of cations cation reaction with NaOH(aq) NH

aluminium, Al

white ppt. soluble in excess white ppt. insoluble in excess ammonium, NH

no ppt. ammonia produced on warming barium, Ba

faint white ppt. is observed unless [Ba

] is very low no ppt. calcium, Ca

white ppt. unless [Ca

] is verylow no ppt. chromium( III), Cr

grey-green ppt. soluble in excess giving dark green solution grey-green ppt. insoluble in excess copper( II), Cu

pale blue ppt. insoluble in excesspale blue ppt. soluble in excess giving dark blue solution iron( II), Fe

green ppt. turning brown on contact with air insoluble in excess green ppt. turning brown on contact with air insoluble in excess iron( III), Fe

red-brown ppt. insoluble in excessred-brown ppt. insoluble in excess magnesium, Mg

white ppt. insoluble in excesswhite ppt. insoluble in excess manganese( II), Mn

R?ZKLWHSSWUDSLGO\WXUQLQJEURZQ on contact with air insoluble in excess R?ZKLWHSSWUDSLGO\WXUQLQJEURZQ on contact with air insoluble in excess zinc, Zn

white ppt. soluble in excess white ppt. soluble in excess 2 Reactions of anions anion reaction carbonate, CO liberated by dilute acids chloride, Cl

gives white ppt. with Ag

(soluble in NH

) bromide, Br

(partially soluble in NH

) iodide, I

gives pale yellow ppt. with Ag

(insoluble in NH

) nitrate, NO

NH liberated on heating with OH

and Al foil nitrite, NO

NH liberated on heating with OH

and Al foil; GHFRORXULVHVDFLGL?HGDTXHRXV.0Q2 sulfate, SO

gives white ppt. with Ba

(insoluble in excess dilute strong acids); gives white ppt. with high [Ca

] VXO?WHSO

gives white ppt. with Ba

(soluble in excess dilute strong acids); GHFRORXULVHVDFLGL?HGDTXHRXV.0Q2 thiosulfate, S 3 Tests for gases gas test and test result ammonia, NH turns damp red litmus paper blue carbon dioxide, CO gives a white ppt. with limewater hydrogen, H ?pops? with a lighted splint oxygen, O relights a glowing splint

Tests for elements element test and test result iodine, I gives blue-black colour on addition of starch solution Important values, constants and standards Faraday constant F = 9.65 u 10 Avogadro constant L = 6.022 u 10 electronic charge e = ?1.60 u 10?19 molar volume of gas V at room conditions ionic product of water K = 1.00 u 10?14 To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Group The Periodic Table of Elements hydrogen 1.0 He helium 4.0 12131415161718 34567891011123Li lithium 6.9 beryllium 9.0 atomic number atomic symbolKey name relative atomic mass sodium 23.0 magnesium 24.3 potassium 39.1 calcium 40.1 rubidium 85.5 strontiu m 87.6 caesium 132. 9 barium 137.3 francium Ra radium boron10.8 13 Al aluminium 27.0 31 Ga gallium 69.7 49 In indium 114.8 thallium 204.4 carbon 12.0 14 Si silicon 28.1 32 Ge germanium 72.6 50 Sntin 118.7 82 Pb lead 207.2 titanium 47.9 40 Zr zirconium 91.2 72 Hf hafnium178. 5 rutherfordium vanadium 50.9 41 Nb niobium 92.9 73 Ta tantalum 180.9 105 Db dubnium chromium 52.0 42 Mo molybdenum 95.9 74 W tungste n 183.8 106 Sg seaborgium manganese 54.9 43 Tc technetium rhenium 186. 2 107 Bh bohrium iron 55.8 44 Ru ruthenium 101.1 76 Os osmium 190.2 108 Hs hassium Co cobalt 58.9 45 Rh rhodium 102.9 iridium192.2 109 Mt meitnerium nicke l58.7 46 Pd palladium 106. 4 platinum 195. 1 110 Ds darmstadtium copper 63.5 47 Ag silver 107. 9 79 Au gold 197. 0 111 Rg roentgenium zinc 65.4 48 Cd cadmium 112.4 80 Hg mercury 200. 6 112 Cn copernicium flerovium livermorium nitrogen 14.0 phosphorus 31.0 33 As arsenic 74.9 51 Sb antimony 121.8 bismuth 209.0 oxygen 16.0 sulfur 32.1 34 Se selenium 79.0 52 Te tellurium 127.6 84 Po polonium fluorine 19.0 17 Cl chlorine 35.5 35 Br bromine 79.9 iodine 126.9 Ne neon 20.2 18 Ar argo n39.9 krypto n 83.8 54 Xe xenon131. 3 86 Rn radon nihonium moscovium tennessine oganesson scandium 45.0 yttriu m 88.9 57?71 lanthanoids 89?103 actinoids 57La lanthanum 138.9 89 Ac lanthanoids actinoids actinium Ce cerium 140.1 90 Th thoriu m232.0 praseodymium 140.9 91 Pa protactinium 231.0 neodymium 144.4 uranium 238.0 promethium neptunium samarium 150.4 94 Pu plutonium europium 152.0 95 Am americium gadolinium 157.3 96 Cm curium terbiu m158.9 97 Bk berkelium dysprosium 162. 5 californium holmium 164. 9 99 Es einsteinium erbium 167. 3 100 Fm fermium Tm thulium168. 9 101 Md mendelevium ytterbiu m 173. 1 102 No nobelium lutetium 175.0 lawrencium