GENERAL PRINCIPLES OF CHEMISTRY CHEM 110/CHEM 195 TEST 1

Size: px

Start display at page:

Download "GENERAL PRINCIPLES OF CHEMISTRY CHEM 110/CHEM 195 TEST 1"

Brice Horton
5 years ago
Views:

1 GENERAL PRINCIPLES OF CHEMISTRY CHEM 110/CHEM 195 TEST 1 Date: THURSDAY, 14 March 2013 Total marks: 25 Time: 17h45 18h30 IMPORTANT: Complete this part immediately. Name: Student No: Tutorial Day: Tutorial Venue: Tutor s Name: INSTRUCTIONS: 1. Answer ALL questions. 2. For Section A which contains the multiple choice questions, write your answers on the multiple choice answer sheet and follow the instructions given in the question. 3. Calculators may be used but all working must be shown. 4. The pages of this test must not be unpinned. 5. Your answers for Section B must be written on the question paper in the spaces provided. The left-hand pages may be used for extra space or for rough work. 6. Marks will be deducted for the incorrect use of significant figures and the omission of units. 7. You must write legibly in black or blue ink. Pencils and Tipp-Ex are not allowed. 8. This test consists of pages. Please check that you have them all. 9. A data sheet and a periodic table are provided. Question No. Mark Section Section B A ½ 1½ 5 TOTAL 25 Page 1 of 6

2 SECTION A - Multiple Choice Questions For each of the following questions, select the correct answer from the list provided. There is only one correct answer for each question. Indicate your answer on the multiple choice answer sheet provided. Make a dark heavy mark with HB pencil that fills the block of the appropriate letter completely. 1. Which of the following quantities has three significant figures? (1) A g B dm 3 C nm D g cm A temperature of C, when expressed in Kelvin, would be: (1) A K B K C K D K 3. The density of benzene at 15ºC is g cm -3. The mass of dm 3 of benzene at this temperature will be (1) A g B g C g D g 4. The numbers of neutrons in the element is: (1) A. 56 B. 81 C. 137 D. 193 Page 2 of 6

3 5. What is the oxidation state of Zn in ZnSO 4 is: (1) A. +2 B. +1 C. 0 D The following reaction can be classified as: (1) BaCO 3 (s) BaO(s) + CO 2 (g) A. combination B. decomposition C. combustion D. displacement 7. The empirical formula of ethyl acetate is C 2 H 4 O and has a molecular mass of 88.1 u. It has a molecular formula of: (1) A. C 2 H 4 O B. C 6 H 12 O 3 C. C 4 H 8 O 2 D. C 8 H 16 O 4 8. The coefficients x and y in the equation given below are (1) A. 1 and 3 x H 2 O 2 (aq) y H 2 O(l) + O 2 (g) B. 2 and 2 C. 3 and 2 D. 2 and 4 Page 3 of 6

4 9. How many moles of O 2 (g) are produced in the decomposition of 32.8 g of KClO 3 (s)? (2) 2KClO 3 (s) 2KCl(s) + 3O 2 (g) (molar mass of KClO 3 = g mol -1 ) A mol B mol C mol D mol 10. Calculate the number of atoms in 3.78 g of Al (1) A x atoms B x atoms C x atoms D x atoms 11. The % composition by mass of nitrogen in the painkiller codeine (C 18 H 21 NO 3 ) is (molar mass of codeine = g mol -1 ) (1) A % B % C % D % 12. What is the percent yield of water if 0.90 g of water (molar mass = g mol -1 ) is obtained when mol of butane is burned in excess oxygen? The balanced chemical equation is (2) A % B. 2.0% C. 10% D. 36% 2C 4 H 10 (g) + 13O 2 (g) 8CO 2 (g) + 10H 2 O(g) Page 4 of 6

5 13. What is the molarity of sodium sulfate, Na 2 SO 4 (molar mass = g mol -1 ) if 24.3 g of sodium sulfate is dissolved in enough water to produce ml of solution? (1) A M B M C M D M [15] SECTION B: Full Questions. Answer on the question paper in the space provided. 1. Copper occurs naturally as a mixture of two stable isotopes: 63 Cu ( u, %) and 65 Cu ( u). Calculate the weighted average atomic mass of naturally occurring copper. % ab Cu-65 = = 30.83% (2) AM = % ab/100 x IM ={(69.17/100 x ) + (30.83/100 x )} ½ each = correct substitution = u /2 ½ correct no. of s.f /½ ans. ( -½ incorrect no. of s.f) 2. Write chemical formulae for each of the following compounds: (1½) i) Copper(II) fluoride CuF 2 ½ ii) Magnesium phosphate Mg 3 (PO 4 ) 2 ½ iv) Iron(II) nitrate Fe(NO 3 ) 2 ½ Page 5 of 6

6 3. Name each of the following compounds: (1½) i) Rb 2 O Rubidium oxide ½ ii) P 4 S 10 Tetraphosporous decasulfide ½ iii) AgClO 4 Silver(I) perchlorate ½ 4. Consider the following reaction: 2Al(s) + 3Cl 2 (g) 2AlCl 3 (s) If we begin with mol of aluminum and mol of chlorine, [5] 4.1 What is the limiting reagent in this reaction? (2½) nalcl 3 = nal 2 2 ½ Therefore nalcl 3 produced = mol ½ nalcl 2 = ncl 2 ½ nalcl 2 = ncl 2 x ⅔ = ⅔ x mol = mol ½ 2 3 Therefore Al is the limiting reagent. ½ 4.2 What is the theoretical yield of AlCl 3 (s)? (1½) nalcl 3 = nal = mol ½ Mass of AlCl 3 = nalcl 3 X MAlCl 3 = x g.mol -1 ½= 73.6 g ½ 4.3 Calculate the % yield of AlCl 3 if the actual yield is g? (1) % Yield = actual yield / theoretical yield x 100 = g/73.6 g x 100 ½ = 95.2 % ½ Page 6 of 6

School of Chemistry and Physics Westville Campus, Durban MODEL ANSWER

School of Chemistry and Physics Westville Campus, Durban BARCODE Test 2: Wednesday 9 April 2014 CHEM110: GENERAL PRINCIPLES OF CHEMISTRY Duration: 45 minutes Total Marks: 25 Time: 17:45 18:30 Examiner: