Skip to content
OCR A AS Specimen Paper 2 Q4
Answers available below
Show answer
Question
1
2
3
4
5
6
7
16
17
18
19
20
21
![4 Students work together in groups to identify four different solutions. Each solution contains one of the following compounds: 10ammonium sulfate, (NH4)2SO4potassium bromide, KBr. sodium sulfate, Na2SO4 sodium chloride, NaCl Your group has been provided with universal indicator paper and the following test reagents: silver nitrate solutionbarium chloride solutiondilute ammonia solutionsodium hydroxide solution. (a)* A student in your group suggests the following plan: Describe how you would expand this plan so that all four solutions could be identified using a positive test result. You should provide observations and conclusions that would enable your group to identify all four solutions.Add about 1 cm depth of each solution into separate test-tubes.Add a few drops of barium chloride solution to each test-tube.A white precipitate will show which solutions contain sulfate ions.Two of the solutions will form a white precipitate. Specimen . . . . . . . . .OCR 2014 H032/02<br />
11 . . . .[6] (b) Solid barium chloride has a high melting point. Barium chloride dissolves in water to form a solution that can be used to test for sulfate ions. (i) Draw a dot-and-cross diagram to show the bonding in solid barium chloride. Show outer electrons only. Specimen (ii) A solution of barium chloride can be made in the laboratory using dilute hydrochloric acid. Suggest a compound that can be reacted with hydrochloric acid to make barium chloride. . [2] [1]OCR 2014 H032/02 Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/Specimen_QP_-_Paper_2_OCR_Chemistry_A_AS-Level_4-0.jpg)
![H032/02 Question (a)* Mark Scheme June 20XX Guidance Indicative scientific points may include Details of tests To identify sulfates:Ammonium ion test: on the sulfates already identified; warm with NaOH(aq) followed byUniversal indicator test: use of moist indicator paper on (ammonia) gas; correct observation (alkaline gas/high pH/blue or purple) for identification of (NH4)2SO4, and by default of Na2SO4. To identify halides:Halide ion test: addition of silver nitrate solution to remaining two solutions; correct observation (white precipitate/cream precipitate) followed bySolubility of precipitate: addition of dilute ammonia solution to halide precipitates; correct observation (silver chloride dissolves) enabling identification of NaCl and by default of KBr. Answer Marks Please refer to the marking instructions on page 4 of this mark scheme for guidance on how to mark this question. Level 3 (56 marks) Describes full details of all of the test procedures and observations that allows all four compounds identified There is a well-developed line of reasoning and the method is clear and logically structured. The information presented is relevant and substantiated by observations from the tests described. Level 2 (34 marks) Describes most of the tests in some detail including the observations that allows all four compounds to be identified. There is a line of reasoning presented and the method has some structure. The information presented is in the most-part relevant and supported by some evidence of observations from the tests described. Level 1 (12 marks) Describes some of the tests but lacks details and observations to allow the identification of all four compounds The information is basic and the method lacks structure. The information is supported by limited evidence of the observations, the relationship to the evidence may not be clear. 0 marks No response or no response worthy of credit. Specimen 12 P M T<br />
H032/02 Question (i) (b) (ii) Mark Scheme June 20XX Guidance For the first mark, if eight electrons are shown in the cation then the extra electron in the anion must match the symbol chosen for electrons in the cation IGNORE inner shell electrons Circles not essential ALLOW One mark if both electron arrangement and charges are correct but only one Cl is drawn allow 2[Cl] (Bracket not required) Answer Marks Specimen Total Barium ion with no (or eight) electrons AND two chloride ions with correct dot-and-cross octet (cid:57) Correct charges (cid:57) Barium hydroxide OR barium oxide OR barium carbonate (cid:57) ALLOW Ba(OH)2 OR BaO OR BaCO3 13 P M T<br />](https://learnah.org/wp-content/uploads/2018/08/Specimen_MS_-_Paper_2_OCR_Chemistry_A_AS-Level_4-0.jpg)
