Have you ever grown potatoes? Do you know how much money you need to invest to grow one kg of potatoes? You can make it cheaper if you don't use fertilizers, but how will that affect your crop? Will you get less potatoes? Does it pay off to buy fertilizers or not? At what cost will you sell your potatoes? Obviously, you can't sell them for the same amount of money you've invested to grow them, you need to earn something too. Even nowadays there are many examples of biology influencing economics. Back in the days of feudalism when arable land was the most valuable possession and the main source of income, knowledge about plants and how all the biotic and abiotic factors affect their growth were essential. Rounding of to three significant figures, we have q = 1.32 x 10 4 J or 13.Did you notice both economics and ecology have the same prefix, eco- ? It is derived from Greek word οἶκος (oikos) which means house or home. Q heating is calculated by the formula we have already used several times: The overall heat of this process then is: Therefore, there are two stages in this process 1) heating the ice to 0 oC, 2) melting the ice. This is not the case here because the ice is at -15.0 oC and before melting, it needs to be first warmed to 0 oC. We mentioned in the previous problem, that since the ice/water is already at 0 oC (melting/freezing temperature), the added heat does not change the temperature of the ice and water mixture, but rather it is used for the transition from solid to liquid. ΔE rxn = 18.2 kJ/0.00633 mol = 2.88 x 10 3 kJ/molĪlternatively, we can set up a cross-multiplication correlation: N(C 4H 10) = 0.367 g/58.0 g/mol = 0.00633 molĪnd after this, we divide the heat of the reaction by the number of moles of butane, to get the heat of the reaction per mole of butane: To find the number of moles, we use the mas and molar mass of butane: To get ΔE rxn per mole of butane, we need to divide q rxn by the number of moles that actually reacted. This is the change in the internal energy of the reaction for that specific amount of butane that was burned.
Since the reaction occurs under conditions of constant volume, q rxn = ΔE rxn, so we need to calculate the q cal using the following formula: This means, the heat goes from the reaction to the calorimeter and assuming there is no heat loss, the heat released by the reaction is equal to the heat absorbed by the calorimeter:
Because the combustion of butane increased the temperature of a bomb calorimeter, it is an exothermic reaction.
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