Question

Combustion reactions 1) A standard chocolate bar has approximately 20 g of sugar in the form of sucrose (C12H22011). Metabolism can be regarded as a drawn-out, multi-step combustion reaction, thus we can model the energy obtained from the sucrose in a chocolate bar as follows: C2H220116 +1202(g) → 12CO2(g) + 11H2O(1) a) Calculate how many Calories (Cal, what you see on product packaging) results from the combustion of 20 g of sucrose. AHºrn = -5635 kJ/mol. (Note: 1 Cal = 1 kcal, and I cal = 4.18 J) b) Using the energy from this combustion to heat 18 mL of water (fits in the palm of your hand), calculate the change in temperature of the water. For simplicity, ignore the resulting phase change and use the heat capacity and density of liquid water, 4.18 J/g °C and 1 g/mL.

Answer 1

a) Molecular mass of sucrose Co Haz Ou = (6X12+ 22X1 + 11X16) q - 270g 903 2Tog = 0.07407 no. of moles of sucrose = w (given weight) - M (molecular weight) ce ton -0.07407 SHE -5635 kJ/mol X 0.07407 E-417,41 kJ Calorie released = .417.4x 10° x de 417.4x10° x Clutte call 4.18 417.4 kcal = 4:18 99.86 Cal. Aug mass of 18mL of water = volume. x density = 18 ml x 1g/mL - 189 AH = m Cp DT 417.41X103 J = 18 X418 (T-27) =) (1-21) = 417.41X103 18 04.18 = 554.77 T -581.77°C 1