Tutoriaal 6 GW.pdf - Chemie 124 Chemistry 124 Tutoriaal 6...

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Chemie 124 Chemistry 124 Tutoriaal 6 GROEPWERK Tutorial 6 GROUP WORK 2015 Van & Voorl. Surname & Initials MEMO Studentnommer: Student number: Demi: Groep/Dag Group/Day A B M D/T W V/F PUNT MARK / 10 Antwoorde vir die volgende vrae word in die groepe uitgewerk. ELKE STUDENT moet SY EIE kopie INHANDIG om gemerk te word. / Solutions to the following questions are to be worked out in groups. EACH STUDENT is to HAND IN THEIR OWN copy of the answers to be marked. 1. 'n Blok yster (75.5 g) by 78.8 °C word in water (450 mL) by 18.8 °C gedompel. / A block of iron (75.5 g) at 78.8 °C is immersed into water (450 mL) at 18.8 °C. (i) Bepaal die ewewigstemperatuur van beide die ysterblok en die water, gegee: / Determine the equilibrium temperature of both the iron block and the water, given: C H2O = 4.18 J/g°C en / and C Fe = 0.45 J/g°C Note the equilibrium temperature for both H 2 O and Fe will be the same T final (T f ) Warmte vloei van die warm yster na die water: q Fe = q H2O [3]
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Chemie 124 Chemistry 124 Tutoriaal 6 GROEPWERK Tutorial 6 GROUP WORK 2015 (ii) Bereken Δ T vir die yster blok en die water, en bespreek hoekom die verandering so anders vir water is in vergelyking met dié vir yster. / Determine Δ T for the iron block and for the water, and discuss why the change observed for water is so different compared to that for the iron. (i.e. temperature decreased) (i.e. temperature increased) Water has a much higher specific heat capacity; it takes at least 9 more energy to change the temp of 1g of water by 1°C compared to Fe, in addition the mass of water is appr. 6 that of Fe. [2] 2. Deur gebruik te maak van die eksperimenteel-bepaalde standaard entalpie veranderinge vir die reaksies 1, 2 en 3 hieronder gegee, bereken die molêre entalpieverandering vir die vorming van B 2 O 3 (s) uit sy elemente. / Using the experimentally-determined standard enthalpy changes for the reactions 1, 2 and 3 given below, calculate the molar enthalpy change for the formation of B 2 O 3 (s) from its elements. ΔH° (kJ) 1. B(s) + H 2 (g) + O 2 (g) H 3 BO 3 (aq) 1077 2. B 2 O 3 (s) + 3H 2 O(l) 2H 3 BO 3 (aq) 17.4 3. H 2 (g) + ½O 2 (g) H 2 O(l) 285.8 Target reaction: 2 B (s) + 3/2 O 2 (g) B 2 O 3 (s) ΔH° (kJ) 1. x2 2 B(s) + 3 H 2 (g) + 3 O 2 (g) 2 H 3 BO 3 (aq) 2154 2. reverse 2 H 3 BO 3 (aq) B 2 O 3 (s) + 3 H 2 O(l) + 17.4 3. x3 and reverse 3 H 2 O(l) 3 H 2 (g) + 3/2 O 2 (g) + 857.4 2 B(s) + 3/2 O 2 (g) B 2 O 3 (s) 1279.20 [4]
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Chemie 124 Chemistry 124 Tutoriaal 6 GROEPWERK Tutorial 6 GROUP WORK 2015 3.
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