Answer:
C
Explanation:
4× CH2 = C4H8
70 Determine the number of moles of copper in the bracelet. [1]
71 Show a numerical setup for calculating the amount of heat released by the bracelet as it cooled on the desk. [1]
72 Explain, in terms of chemical activity, why copper is a better choice than iron to make the bracelet. [1]
69. The student's skin was obviously warmer than the initial temperature of the bracelet. According to the second law of thermodynamics, heat transfers from a higher temperature to a lower temperature. Hence, heat transfers from the student's skin to the bracelet warming up the bracelet.
70. To determine number of moles of copper:
Given mass=30.1 grams
Molar mass= 63.55 g/mol
Thus, the number of moles of copper is 0.4736.
71. Calculating the amount of heat released:
ΔH( heat released) = m Cp(ΔT)
= 30.1g(0.385 J/g. K)(33-19)K
ΔH= 162.23J
Thus, the amount of heat released is 162.23 J.
72. Copper is chemically less active than iron.
Copperdoes notdisplace iron from its solution since it is less reactive than iron. A more reactive metal displaces a less reactive metal from its solution.
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