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. moles of copper=mass of copper/molar mass of copper
=30.1g/(63.55g/mol)= 0.4736 moles Cu
71. Delta H( heat released) = mCp(deltaT) = 30.1g(0.385 J/gK)(33-19)K = 162.23J
72. Copper is chemically less active than iron.
Explanation:
The given data is as follows.
q = 69.0 kJ = 69000 J (as 1 kJ = 1000 J),
mass (m) = 8.10 kg = 8100 g (as 1 kg = 1000 g)
= (33.9 + 273) K = 306.9 K
C = 4.18 J/gK
As we know that the relation between heat and change in temperature is as follows.
q = 
Putting the values into the above formula to calculate the final temperature as follows.
q =
69000 J = 
69000 J = 
= 2.037 K
= (2.037 + 306.9) K
= 308.9 K
or, = 309 K (approx)
Thus, we can conclude that the new temperature of the water bath is 309 K.
Answer:
Germanium.
Explanation:
In a neutral atom: the number of protons = the number of electrons.
Atomic number of a neutral atom = number of electrons = number of protons.
- Phosphorous is an element with atomic number 15 and thus contains 15 electrons and 15 protons.
- Cobalt is an element with atomic number 27 and thus contains 27 electrons and 27 protons.
- <em>Germanium is an element with atomic number 32 and thus contains 32 electrons and 32 protons.</em>
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- Sulfur is an element with atomic number 16 and thus contains 16 electrons and 16 protons.
