The number of Calories in food items were originally determined by combusting the food, and measuring the heat released by the food in a calorimeter (see figure 12.9 in your textbook for a visual). Let’s say you place a 115 g peeled banana in a calorimeter that contains 850.0 mL of water. You observe that after burning the banana, the water temperature increases by about 120 ℃. The specific heat capacity for liquid water is 4.184 J/g-℃. 1 calorie is defined as the energy required to raise the temperature of 1 gram of water 1 ℃. The density of liquid water is about 1.00 g/mL. a) What is the heat in kJ released by the combustion of the banana? ( b) How many Calories are in this banana? (In chemistry 1 Calorie (capital C) = 103 calories (lowercase C) = 1 kilocalorie). Show all steps of your work. c) How many Calories would you expect a 50.0 g banana to be?
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
The number of Calories in food items were originally determined by combusting the food, and measuring the heat released by the food in a calorimeter (see figure 12.9 in your textbook for a visual). Let’s say you place a 115 g peeled banana in a calorimeter that contains 850.0 mL of water. You observe that after burning the banana, the water temperature increases by about 120 ℃. The specific heat capacity for liquid water is 4.184 J/g-℃. 1 calorie is defined as the energy required to raise the temperature of 1 gram of water 1 ℃. The density of liquid water is about 1.00 g/mL.
a) What is the heat in kJ released by the combustion of the banana? (
b) How many Calories are in this banana? (In chemistry 1 Calorie (capital C) = 103 calories (lowercase C) = 1 kilocalorie). Show all steps of your work.
c) How many Calories would you expect a 50.0 g banana to be?
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