CLASS TEST GRADE PHYSICAL SCIENCES: CHEMISTRY Test 6: Chemical change MARKS: 45 TIME: hour INSTRUCTIONS AND INFORMATION. Answer ALL the questions. 2. You may use non-programmable calculators. 3. You may use appropriate mathematical instruments. 4. Number the answers correctly according to the numbering system used in this question paper. 5. Data sheets are attached for your use. 6. Wherever motivation, discussion, et cetera is required, write brief answers.
SECTION A QUESTION : ONE-WORD ANSWERS Give ONE word or term for each of the following descriptions. Write only the word or term next to the question number (..2).. The amount of substance containing 6,023 0 23 particles. ().2 The reactant that is used up first in a chemical reaction. () [2] QUESTION 2: FALSE STATEMENTS Correct the following FALSE statements. Write the correct statement next to the question number (2. 2.2). 2. Activation energy is the energy that the reactants possess before a reaction takes place. (2) 2.2 In the reaction HCO 3 (aq) + OH (aq) H 2 O(aq) + CO 3 2 (aq), the conjugate bases are OH and H 2 O. (2) [4] QUESTION 3: MULTIPLE-CHOICE QUESTIONS Choose the correct answer to the following questions. Write only the letter (A D) next to the question number (3. 3.2). 3. Which one of the following reactions is a redox reaction? A B C KCl(aq) + AgNO 3 (aq) AgCl(s) + KNO 3 (aq) HNO 3 (aq) + KOH(aq) KNO 3 (aq) + H 2 O(l) 2H 2 S(aq) + H 2 SO 3 (aq) 3S(s) + 3H 2 O(l) D CuSO 4 (aq) Cu 2+ (aq) + SO 4 2 (aq) (2) Maskew Miller Longman, Focus on Physical Sciences Grade Test 6: Chemical change Page 2 of 7
3.2 Consider the following reaction. CO 2 (g) + C(s) + heat 2CO(g) The graph of potential energy versus course of reaction for the reaction is... A B C D (2) [4] TOTAL SECTION A: 0 Maskew Miller Longman, Focus on Physical Sciences Grade Test 6: Chemical change Page 3 of 7
SECTION B INSTRUCTIONS AND INFORMATION. The formulae and substitutions must be shown in ALL calculations. 2. Round off your answers to TWO decimal places where applicable. QUESTION 4 4. The formula for potassium dichromate is K 2 Cr 2 O 7. How many chromium atoms are there in 47 grams of potassium dichromate? (3) 4.2 Calcium phosphate Ca 3 (PO 4 ) 2 is a plant nutrient that supplies phosphorus. Calculate the percentage composition of phosphorus in this compound. (3) 4.3 Ammonium nitrate is used in fireworks. When gently and cautiously heated, water vapour is formed, along with another gaseous product. The gaseous product is 63,6% nitrogen and 36,4% oxygen. The molecular mass of this gaseous product is 44 g mol. Determine the empirical formula of this product. (5) [] QUESTION 5 Powdered aluminium (2,7 g) reacts with solid iodine (2,7 g) to produce aluminium iodide, which is used in organic reactions. The equation for the reaction is: 2Al(s) + 3I 2 2AlI 3 (s) 5. Which reactant is the limiting reagent? Explain how you arrived at your answer. (3) 5.2 What mass of the other reactant remains unreacted? (3) 5.3 Calculate the mass of aluminium iodide formed. (3) [9] Maskew Miller Longman, Focus on Physical Sciences Grade Test 6: Chemical change Page 4 of 7
QUESTION 6 4,3 g of sodium carbonate crystals is dissolved in water and the solution is made up to 500 cm 3 (Na 2 CO 3.0H 2 O). 6. Calculate the concentration of the sodium carbonate solution. (4) All the sodium carbonate solution reacts with excess hydrochloric acid. 6.2 Write down a balanced equation for this reaction. (2) 6.3 Calculate the volume of CO 2 produced in this reaction at STP. (3) [9] QUESTION 7 7. Classify the following organic reactions. 7.. C 2 H 6 + Br 2 C 2 H 5 Br + HBr () 7..2 CH 3 CH 2 Cl(l) + KOH(alcohol) C 2 H 4 (g) + KCl(aq) + H 2 O(l) (2) 7..3 CH 3 CH 2 OH(g) CH 2 CH 2 (g) + H 2 O(g) () 7.2 What type of reaction occurs in the production of each of the following? 7.2. plastics () 7.2.2 margarine () [6] TOTAL SECTION B: 35 GRAND TOTAL: 45 Maskew Miller Longman, Focus on Physical Sciences Grade Test 6: Chemical change Page 5 of 7
DATA FOR PHYSICAL SCIENCES GRADE CHEMISTRY PHYSICAL CONSTANTS NAME SYMBOL VALUE Avogadro s constant N A 6,02 0 23 mol Molar gas constant R 8,3 J K mol Standard pressure p θ,03 0 5 Pa Molar gas volume at STP V m 22,4 dm 3 mol Standard temperature T θ 273 K FORMULAE p V T = p V 2 2 T pv = nrt 2 n = m M c = n V c = MV m n a nb = c V a a c b V b Printed with permission, National Department of Education Maskew Miller Longman, Focus on Physical Sciences Grade Test 6: Chemical change Page 6 of 7
(I) H 3 Li 7 Na 23 9 K 39 37 Rb 86 55 Cs 33 87 Fr 2 (II) 4 Be 9 2 Mg 24 20 Ca 40 38 Sr 88 56 Ba 37 88 Ra 226 THE PERIODIC TABLE OF ELEMENTS 3 4 5 6 7 8 9 0 2 3 (III) 5 B 4 (IV) 5 (V) 6 (VI) 7 (VII) 8 (VIII) 2 He 4 0 Ne 20 8 Ar 40 36 Kr 84 54 Xe 3 86 Rn,0 2,,5 2,0 2,5 3,0 3,5 2,8 3,0 4,0 3 Al 6 C 2 4 Si 7 N 4 5 P 8 O 6 6 S 32 34 Se 9 F 9 7 Cl 35,5 35 Br 80 53 I 27 85 At 0,9,2,5 2, 2,5 2 Sc 45 39 22 Ti 27 3 28 32 Ge 73 50 Sn 3 33 As 75 5 Sb 0,8,0,3,5,6 48 40 23,6 V 5 4 24,5 Cr 52 42 25 Mn 55 43 26 Fe 56 44 27 Co 59 45 28 Ni 59 46 29,6 Cu 63,5 47 30,6 2,0 2,4 Y 89 57 Zr Zn 65 48 Ga 70 49 79 52 Te 28 84 Po 0,8,0,2,4 2,2 2,2 2,2,7,7 2, 2,5 2,5 La 39 89 9 72 Hf Nb 92 73 Mo 96 74 Tc Ru 0 76 Rh 03 77 Pd 06 78 Ag 08 79 Cd 2 80 In 5 8 9 82 Pb 207 22 83 Bi 209 0,7 0,9,6 79 Ta 8 W 84 75 2,0 KEY Atomic number Ac Re 86 29 Cu 63,5 Electronegativity Symbol Os 90 Ir 92 Pt 95 Au 97 Hg 20 Tl 204 58 Ce 40 59 Pr 4 60 Nd 44 6 Pm 62 Sm 50 63 Eu 52 64 Gd 57 65 Tb 59 66 Dy 63 90 Th 232 9 Pa 92 U 238 93 Np 94 Pu 95 Am 96 Cm Printed with permission, National Department of Education 97 Bk 98 67 Ho 65 99 Es 68 Er 67 00 69 Tm 69 0 Md 70 Yb 73 02 No 7 Lu 75 03 Lr 0,7 0,9 Approximate relative atomic mass Maskew Miller Longman, Focus on Physical Sciences Grade Test 5: Atomic nuclei Page 7 of 7