Sl Ib Chemestry May 2007
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Publicado: 20 de febrero de 2013
M10/4/CHEMI/SP2/ENG/TZ1/XX+
22106111
CHEMISTRY STANDARD LEVEL PAPER 2 Wednesday 12 May 2010 (afternoon) 1 hour 15 minutes INSTRUCTIONS TO CANDIDATES Write your session number in the boxes above. Do not open this examination paper until instructed to do so. Section A: answer all of Section A in the spaces provided. Section B: answer one question from Section B. Write your answers on answersheets. Write your session number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided. • At the end of the examination, indicate the numbers of the questions answered in the candidate box on your cover sheet and indicate the number of sheets used in the appropriate box on your cover sheet.
• • • •
Candidate session number 0 02210-6111
11 pages © International Baccalaureate Organization 2010
0111
– 2 – SECTION A Answer all the questions in the spaces provided. 1.
M10/4/CHEMI/SP2/ENG/TZ1/XX+
Brass is a copper containing alloy with many uses. An analysis is carried out to determine the percentage of copper present in three identical samples of brass. The reactions involved in this analysis are shown below. Step 1: Cu (s) 2HNO3 (aq) 2H + (aq) Step 2: 4I (aq) 2Cu 2+ (aq) Step 3: I 2 (aq) 2S2 O32 (aq) (a) (i) Cu 2+ (aq) 2NO 2 (g) 2H 2 O (l)
2CuI (s) I 2 (aq) 2I (aq) S4 O6 2 (aq) [2]
v Deduce the change in the oxidation numbers of copper and nitrogen in step 1.
Copper:.................................................................. Nitrogen: .................................................................. (ii) Identify the oxidizing agent in step 1. .................................................................. (b) A student carried out this experiment three times, with three identical small brass nails, and obtained the following results. Mass of brass = 0.456 g 0.001 g Titre Initial volume of 0.100 mol dm–3 S2O32– ( 0.05 cm 3 ) Final volume of 0.100 mol dm–3 S2O32– ( 0.05 cm 3 ) Volume added of 0.100 mol dm–3 S2O32– ( 0.10 cm 3 ) Average volume added of 0.100 mol dm–3 S2O32– ( 0.10 cm 3 ) 1 2 3 [1]
0.00 0.00 0.00 28.50 28.60 28.40 28.50 28.60 28.40 28.50
(This questioncontinues on the following page)
2210-6111
0211
– 3 – (Question 1 continued) (c) (i)
M10/4/CHEMI/SP2/ENG/TZ1/XX+
Calculate the average amount, in mol, of S2O32– added in step 3. .................................................................................................................................... .................................................................. ..................................................................
[2]
(ii) Calculate the amount, in mol, of copper present in the brass. .................................................................. .................................................................. (iii) Calculate the mass of copper in the brass. .................................................................. .................................................................. (iv) Calculate the percentage by mass of copper in the brass. .................................................................. ..................................................................
[1]
[1]
[1](v) The manufacturers claim that the sample of brass contains 44.2 % copper by mass. Determine the percentage error in the result. [1] .................................................................. .................................................................. With reference to its metallic structure, describe how brass conducts electricity....
22106111
CHEMISTRY STANDARD LEVEL PAPER 2 Wednesday 12 May 2010 (afternoon) 1 hour 15 minutes INSTRUCTIONS TO CANDIDATES Write your session number in the boxes above. Do not open this examination paper until instructed to do so. Section A: answer all of Section A in the spaces provided. Section B: answer one question from Section B. Write your answers on answersheets. Write your session number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided. • At the end of the examination, indicate the numbers of the questions answered in the candidate box on your cover sheet and indicate the number of sheets used in the appropriate box on your cover sheet.
• • • •
Candidate session number 0 02210-6111
11 pages © International Baccalaureate Organization 2010
0111
– 2 – SECTION A Answer all the questions in the spaces provided. 1.
M10/4/CHEMI/SP2/ENG/TZ1/XX+
Brass is a copper containing alloy with many uses. An analysis is carried out to determine the percentage of copper present in three identical samples of brass. The reactions involved in this analysis are shown below. Step 1: Cu (s) 2HNO3 (aq) 2H + (aq) Step 2: 4I (aq) 2Cu 2+ (aq) Step 3: I 2 (aq) 2S2 O32 (aq) (a) (i) Cu 2+ (aq) 2NO 2 (g) 2H 2 O (l)
2CuI (s) I 2 (aq) 2I (aq) S4 O6 2 (aq) [2]
v Deduce the change in the oxidation numbers of copper and nitrogen in step 1.
Copper:.................................................................. Nitrogen: .................................................................. (ii) Identify the oxidizing agent in step 1. .................................................................. (b) A student carried out this experiment three times, with three identical small brass nails, and obtained the following results. Mass of brass = 0.456 g 0.001 g Titre Initial volume of 0.100 mol dm–3 S2O32– ( 0.05 cm 3 ) Final volume of 0.100 mol dm–3 S2O32– ( 0.05 cm 3 ) Volume added of 0.100 mol dm–3 S2O32– ( 0.10 cm 3 ) Average volume added of 0.100 mol dm–3 S2O32– ( 0.10 cm 3 ) 1 2 3 [1]
0.00 0.00 0.00 28.50 28.60 28.40 28.50 28.60 28.40 28.50
(This questioncontinues on the following page)
2210-6111
0211
– 3 – (Question 1 continued) (c) (i)
M10/4/CHEMI/SP2/ENG/TZ1/XX+
Calculate the average amount, in mol, of S2O32– added in step 3. .................................................................................................................................... .................................................................. ..................................................................
[2]
(ii) Calculate the amount, in mol, of copper present in the brass. .................................................................. .................................................................. (iii) Calculate the mass of copper in the brass. .................................................................. .................................................................. (iv) Calculate the percentage by mass of copper in the brass. .................................................................. ..................................................................
[1]
[1]
[1](v) The manufacturers claim that the sample of brass contains 44.2 % copper by mass. Determine the percentage error in the result. [1] .................................................................. .................................................................. With reference to its metallic structure, describe how brass conducts electricity....
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