1. On Exam 1, you were asked to consider the film The Martian, in which a chemis
ID: 1043668 • Letter: 1
Question
1. On Exam 1, you were asked to consider the film The Martian, in which a chemist harnesses energy associated with the reaction between table sugar and liquid oxygen, shown in the balanced reaction below. Let's do it again! aH2 011(6)+ 12 0,(0) 12 co2(g)+ 11 H,0 (g) AH m-5155.7 k/ b. (2 points) Calculate the heat given off by this reaction when performed with 200.0 mL liquid oxygen (d = 1.141 mL) and 200.0 grams of sugar (342.3 g/mol).1 2 32. m ii. -2685 ku ?2Big@-3012 kjadagsgr K 5LEJy :. o.SSy3m. s roe A iv. -3064 k 0? (3 points) The reaction in part b occurs in a cannister, originally at 20.00 °C. What is final temperature in the cannister after the reaction (assume that by c. s.gay l now, it contains only 115.8 g water and 308.6 g carbon ..gY /5.029 dioxide)? Hint: first, solve for change in temperature. Cs co, 0.846 g °c g °CExplanation / Answer
calculate the moles of sugar with
moles = mass / molar mass
moles of sugar = 200 / 342.3 = 0.58428 moles of sugar
do the same with liquid, calculate mass with
mass = density * volume
mass = 1.141 g/ml * 200 ml = 228.2 grams of oxygen
calculate moles (molar mass of oxygen is 16, molar mass of O2 is 32)
moles = 228.2 / 32 = 7.13 moles
1 mole of sugar requires 12 moles of sugar so
0.584 * 12 = 7.008 moles of O2 required, O2 is in excess because we have more amount than this
sugar is the limiting reactant, we must make calculations with the information about sugar:
multiply 0.584 by 5155.7 to get : 3012.38 KJ
b) lets calculate the mass percent of water and CO2
total mass is 115.8 + 308.6 = 424.4 grams
fraction water = 115.8 / 424.2 = 0.273
fraction CO2 = 308.6 / 424.2 = 0.727
calculate average Cp using this information:
Cp = 0.846 * 0.727 + 1.864*0.273 = 1.1239 J / g C
apply the equation
Heat = mass * heat capacity (which is cp) * (Tf - Ti)
so :
3012.32 = 424.2 * 1.1239 * (Tf - 20)
3012.32 = 476.758 * (Tf - 20)
3012.32/476.758 = 6.318 = Tf - 20
Tf = 20 + 6.318 = 26.318 Celsius
heat lost by the reaction is equal to the heat gained by the canister
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