in which 10.0 g of sucrose, C12H22O11, was burned in a bomb calorimeter with a h
ID: 823526 • Letter: I
Question
in which 10.0 g of sucrose, C12H22O11, was burned in a bomb calorimeter with a heat capacity of 7.50 kJ/degreeC. The temperature increase inside the calorimeter was found to be 22.0 degreeC. Calculate the change in internal energy, DeltaE, for this reaction per mole of sucrose. A calorimeter contains 24.0mL of water at 11.0degreeC . When 2.50g of X (a substance with a molar mass of 65.0g/mol) is added, it dissolves via the reaction and the temperature of the solution increases to 27.0degreeC . Calculate the enthalpy change, AH. for this reaction per mole of X. Assume that the specific heat of the resulting solution is equal to that of water that density of water is 1.00 g/mL, and that no heat is lost to the calorimeter itself, nor to the surroundings.Explanation / Answer
(1) C12H22O11 + 12 O2 => 12 CO2 + 11 H2O
Heat released by reaction = heat capacity x temperature change of calorimeter
= 7.50 x 22.0 = 165 kJ
Moles of sucrose = mass/molar mass of sucrose
= 10.0/342.3 = 0.029214 mol
Delta E = -heat released/moles of sucrose
= -165/0.029214
= -5648 kJ/mol = -5.65 x 10^3 kJ/mol
(2) X(s) + H2O(l) => X(aq)
Mass of water = volume x density
= 24.0 x 1.00 = 24.0 g
Heat released by reaction = mass x specific heat x temperature change of solution
= (24.0 + 2.50) x 4.18 x (27.0 - 11.0)
= 1772.32 J
Moles of X = mass/molar mass of X
= 2.50/65.0 = 0.0384615 mol
Delta H = -heat released/moles of X
= -1772.32/0.0384615
= -46080 J/mol = -46.1 kJ/mol
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