chm1020-w6-lab-assignment-part-a

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1010

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Chemistry

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Dec 6, 2023

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Name(s):________________________________CHM 1020 W6 | Part A Week 6 Assignment – Part A Multiple Choice : 1) The law of conservation of energy states that ________. A) the energy of the reactants and products in a chemical reaction are always equal B) all chemical reactions are reversible C) energy can be created, but not destroyed D) energy cannot be created or destroyed 2) Which of the following energy quantities is equivalent to 578 J? A) 5.78 × 10 5 kJ C) 0.138 kcal B) 138 kcal D) 1.38 × 10 5 kcal 3) Which of the following energy quantities is equivalent to 11.9 kcal? A) 1.19 × 10 5 cal C) 49.8 kJ B) 49.8 J D) 2.84 × 10 3 kJ 4) Which of the following energy quantities is equivalent to 258 Cal? A) 258 cal C) 1080 kJ B) 1080 J D) 6.17 × 10 4 kJ 5) Which quantity represents the largest amount of stored energy? A) 10 grams of fat B) 10 grams of carbohydrate C) 10 grams of protein D) 5 grams of carbohydrate plus 5 grams of protein E) 5 grams of protein plus 5 grams of fat 6) Which bond is the strongest? A) H–Br C) H–F B) H–Cl D) H–I 7) Which bond is the weakest? A) H–Br C) H–F B) H–Cl D) H–I 8) Which term correctly describes a reaction in which the energy of the products is higher than the energy of the reactants? A) Oxidation-reduction C) Exothermic B) Endothermic D) Combustion 9) Consider the reaction: C 3 H 8 ( g ) + 5 O 2 ( g ) → 3 CO 2 ( g ) + 4 H 2 O( g ), where Δ H = –531 kcal. Which statement concerning this reaction is true? A) Heat is absorbed. B) The bonds formed in the products are stronger than the bonds broken in the reactants. C) The products are higher in energy than the reactants. D) The reaction is endothermic. Page 1 of 3
Name(s):________________________________CHM 1020 W6 | Part A Short Answer / Problem Solving (Show your work): 10) A chemical reaction requires 31.39 kJ. How many kilocalories does this correspond to? 1kJ = 0.239kcal 31.39 x 0.23g = 7.50221kcal 11) A peanut butter and jelly sandwich contains 9.00 g of fat, 6.00 g of protein, and 25.0 g of carbohydrate. How many Calories does this sandwich provide? Carbs- 4cal/g=4cal x 25 =10 cal Protein- -4cal/g=4x6cal=24 cal Fat- 9cal/g= 9cal x 9= 87cal Total calories = 100+24+87=205cal Page 2 of 3
Name(s):________________________________CHM 1020 W6 | Part A 12) Consider the reaction, C 2 H 4 ( g ) + H 2 ( g ) → C 2 H 6 ( g ), where Δ H = –137 kJ. How many kilojoules are released when 3.5 mol of C 2 H 4 reacts? 1 Mole of reaction of C2H4 releases -137kJ 3.5 mole of reaction of C2H4 will release (-137 x 3.5) kJ = -479.5 kJ 13) Consider the reaction, C 2 H 4 ( g ) + H 2 ( g ) → C 2 H 6 ( g ), where Δ H = –137 kJ. How many kilojoules are released when 55.3 g of C 2 H 4 reacts? Molar Mass=28.05g/mol Moles=mass/molar mass Moles=55.3/28.05=1.971mol Molar enthalpy=-137kJ Kilo joules released = (1.971x-137)=-270.09kJ 14) Watch the following video and complete the calculation to determine the specific heat of the cadmium metal: https://www.youtube.com/watch?v=8gHFaL2990U Mass of cd sample =58.953g Mass of water taken =100g Temp of water, T1 =22˚C Temp of water after sample, T2 = 25˚C The temperature change of water, dT= T2-T1 = 3˚C The heat gained by water, q= m x c x dT = 100 x 4.184 x 3 =1255.2 J Q of cadmium =-1255.2 J Heat will be released by sample 0.284 J/g˚C Page 3 of 3
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