Write your name here (Surname Other names ] Centre Number Candidate Number Pearson Edexcel International GCSE Chemistry Unit:4CHO Paper: 2CR Wednesday 13 June 201 8 - Morning Paper Reference Time: 1 hour 4CHO/2CR You must have: Total Marks Ruler, calculator ] Instructions • Use black ink or ball-point pen. • Fill in the boxes at the top of this page with your name, centre number and candidate number. • Answer all questions. • Answer the questions in the spaces provided - there may be more space than you need. • Show all the steps in any calculations and state the units. • Some questions must be answered with a cross in a box Kl. If you change your mind about an answer, put a line through the box N and then mark your new answer with a cross IX]. Information • The total mark for this paper is 60. • The marks for each question are shown in brackets - use this as a guide as to how much time to spend on each question. Advice • Read each question carefully before you start to answer it. • Write your answers neatly and in good English. • Try to answer every question. • Check your answers if you have time at the end. Turnover > P53147A ©2018 Pearson Education Ltd. 1/1/1/1/1/1/ P 5 3 1 A 1 2 0 Pearson 0 -?!"'1 s ® 0 s<|" s ^|s "51 s ^p 1^ £ x g 0 I .1 r~ s, -Is 0 °' u. §<» ^y SffllS C*J 5|s § s: m I <0 £ o|niS cn|i° ^4 s ^| s m 0 & ^1» g4 s ? ,'^ x in •V '[>. i"^|s|^^|= §'5.1 S "I BT < <7 > 30 •<• s' u s w|T c<S|s ?<5£S §f|s ^ u s CO 'S £, s ml" ^<J^5|^ I SFJ" S^|8 "pl N ^ 0 sfJs 0 LU —I CD s3j^^^ ?^Js I 0 s § a s;2.|s|s £|^|» a:|s 0 z I' ~1 I £ oc >a UJ •$:m a- sSF §£l^ ^jfc UJ u 3: I I S £|S 0 I^l? 86|s (E s I {iii!I i j- -I?- ^ Is & li ^ 31 i ii s •g. s ||s|s^|? QC| 0 I a: I I I il I Ill I il K 61 S s$|s Kj 5 $sls i§ m IE >|s|s ^|^ "»ffl|e w 5 z I" i .1 i ?F|a 5 N I 5 e £|s ^ F 's I I ^1- s ^|s|§ j5|" Ka^js ^ 'I 3 < ;1 E ,1 .1. E c^ 0> ® o5?S 2 51 s &i' ^5? s<3|8 CD<3 s&~js u 5 I 2 [ E n^- j .1. s s^p &F s<3|3 ^1" S3" £ WK> £ z ii r~> ill I n co •* in (0 isi a- M 2 II •""^ i Answer ALL questions. iC 1 The table shows some information about five gases. y sc: < Formula Boiling point 2 Gas c' of molecule in°C z: chlorine Cl -35 2 oxygen -183 e A. 5 carbon monoxide co -191 ft 3 z N -196 nitrogen 2 9 5. H -253 hydrogen 2 Choose gases from the table to answer this question. You may use each gas once, more than once, or not at all. (a) Name the gas that is a compound. t (1) ^ C^bo'<\ mo^voxil c »3r';1 -':;:' (b) Name the gas necessary for rusting to occur. 23' ••'.;> (1) U3; I (c) Name the gas that bleaches moist litmus paper. I (1) I %" .(M^^ 8 (d) Name the gas that has the highest percentage by volume in air. I (1) 8 i i .^ihp^*.. <%. (e) Name the gas that has the highest boiling point. (1) I .(A.b<i.bt.. I (f) Determine the two gases that have the same relative formula mass. i (1) I 1 .^bQy^ I 2.....C-^h^......i?Q/VQ^(i.c. I I (Total for Question 1=6 marks) I ;i 3 Tiirn ni/or ^ 2 A student uses this apparatus to study the rate of the reaction between marble chips and dilute hydrochloric acid. p cotton wool ^ /• 0 § -^ -^y 30 ^ I z -1 3: marble chips ^ dilute hydrochloric acid > g balance •3,30.c<5 s She uses this method. .•'0 ^ place a conical flask on a balance I put 15 g of large marble chips in the flask ^ ^ •A-t add 25 cm3 of dilute hydrochloric acid to the flask •§m :gi record the mass of the flask and contents, and start a timer II record the mass of the flask and contents every 30 seconds until the reaction ends i The equation for the reaction is i m CaCO^s) + 2HCL(aq) -> CaC^(aq) + C0,(g) + Hp(l) M (a) (i) Explain what happens to the mass of the flask and contents during the reaction. 8 (2) s cl^^^^^,,, .^s, Co^ .1^^^^ i • I ji ilTl li (ii) State why the reaction ends, even though some marble chips remain in the flask. ;1) .A].l...&....Ha..........h^....^^-d I IS %; a i§ li 4 I ^ (iii) State how the student would know when the reaction has ended. (1) t I /y^^.., oi:.A.Ji.^.^ .^ 2 t: y u (b) The student plots her results on a grid. s 0.7- ? z H 0.6- ? 3 4 0.5- ~T loss in 0.4 -\ :n mass in g 0.3- I. 0.2- &::. 0.1 - I I jttt •t - TTI 0 I 0 246 8 10 12 14 &i> time in minutes ^ K I (i) At which time is the rate of reaction greatest? ?'? (1) I K A 1 minute I D B 4 minutes ^ C 6 minutes I D D 8 minutes I (ii) The student repeats the experiment with the same volume and concentration i of acid, but with 15 g of smaller marble chips. ' M On the grid, sketch the curve you would expect for this experiment. I (2) M I I I I I I 5 I Ill Tiirn f\\fov (c) Explain how decreasing the concentration of the hydrochloric acid affects the rate of reaction. 0 Refer to particle collision theory in your answer. 0 (3) 3 ^.^.......^L .(?^^L...ih. .11^........s^ I ..^^,^.... j^c^$s.fcL..c0y/S)^ z 1^^^ .^^^^^^^^^^^^ ^ m > (Total for Question 2 = 10 marks) i •;^z i I :1.fiFO I M i M K I I I II i II i I K N s 6 y a: e a: 2 c- z: u e ? 3 z: I ^ I t I. BLANK PAGE I I Ki K! Ki 8U i^/ lU ^ s I It ri I- ii I II^ li i IL 7 Tiiaoyt J^I/A»- & 3 A student is provided with a solution of sodium hydroxide, NaOH, and a solution of 0.0200 mol/dm3 phosphoric(V) acid, H PO^ She does a titration to find the volume of the phosphoric(V) acid that reacts with § 25.0cm3 of the sodium hydroxide. § 2 -I m burette z I ^ § ^ )1 conical flask white tile •o This is the student's method. :Q • add phosphoric(V) acid to a clean burette until it is nearly full i record the burette reading use a measuring cylinder to add 25.0cm3 of the sodium hydroxide to a clean i conical flask ;<:z 1 add a few drops of phenolphthalein indicator to the flask place the flask on a white tile ,i add phosphoric(V) acid from the burette until the indicator changes colour ^ ?m record the burette reading I! wash the flask using distilled water and then dry the flask repeat the titration I i! v%s Issi§ % I li li II II i I I ,"'^.^:.;, s's<y v, ii 8 (a) (I) Name a piece of apparatus that would give a more precise measurement of the volume of sodium hydroxide. (1) I .f'.f..^.... 2 E (ii) Suggest why the student places the flask on a white tile. (1) .....lo.sec...,..tLL....C0k^....A^ s ••••/""•"" ^ ? 3 :i (iii) Give the colour change of the phenolphthalein indicator during the titration. (2) at start...........P,nk- atend . CpWi^S (iv) The student dries the flask after washing it with distilled water. li Suggest why it is not necessary to dry the flask before repeating the titration. I (1) •r':1 ,y^b<. ..(LQQ i^oh..^^ ^'; I2:^: I I i i B 8 it s i; Ii^ II I I•^ I 5$$ IKv <'*-'•..' i ^ s^' II ^ Ill 9 T..»» -*.—.« fc. (b) The diagram shows the student's burette readings for her titration, before and after adding the acid. § 1 22 s 2° -1 m z 2 23 t/1 > before after Use the readings to complete the table, giving all values to the nearest 0.05 cm3. (2) ::<0 burette reading after adding the acid 22.80 ^ I burette reading before adding the acid 1-4S volume in cm3 of acid added Zl-35 I I i i I I s I li I^ I8 I I 1% 8 B II X'K 10 I II (c) Another student does the experiment four times. iC The table shows his results. t t 2 Volume in cm3 of acid added 21.80 21.50 21.35 21.40 c z: Concordant results (/) ^ u E 3 Concordant results are those within 0.20cm3 of each other. ? z- (i) Place ticks in the table to show which results are concordant. I (1) (ii) Use the concordant results to calculate the average (mean) volume of acid added. 7^_So^_2-l-3S^ ^-^o ^ ^l.^-L s I ^ •'..:' 2.1.^f^ 3 I average volume cm 1^ (d) The titration is repeated many times.