ut eegy changes associated with the 4. What effect will making your reaction mix
ID: 557635 • Letter: U
Question
ut eegy changes associated with the 4. What effect will making your reaction mixtures more concentrated have on the heat energy 5. What effect will substituting other reactants in the reaction have? For example, does it reaction and help you avoid any reactions "taking off" or becoming too energetic) changes? make a difference in an acid base reaction which acid or base you use? r Pre-lab Questions A Bic lighter is used to raise the temperature of 100.0 mL of water from 19.5°C to 36.5 °C. In the process 0.143 g of butane (C4H10) are consumed. a. How much heat energy (in Joules) is absorbed by the water? 1. 4Explanation / Answer
a)
volume of water = 100 mL
density of water = 1.00 g / mL
mass of water = volume x density
= 100 x 1
= 100 g
dT = 36.5 -19.5
dT = 17 oC
Cp = 4.184 J / g oC
a)
heat absorbed by the water = Q = m Cp dT
Q = 100 x 4.184 x 17
Q = 7113 J
heat energy absorbed by the water = 7113 J
b)
heat absorbed by the water = heat released by butane = 7113 J
c)
moles of butane = mass / molar mass
= 0.143 / 58.12
= 2.46 x 10^-3
heat combustion of butane = - Q / n
= -7.113 kJ / 2.46 x 10^-3
= -2891 kJ / mol
heat combustion of butane = - 2891 kJ / mol
d)
butane actal combustion enrrgy = 2877 kJ / mol
% error = ( 2891 -2877 / 2877 ) x 100
= 99.5 %
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