A student made a copper bracelet by hammering a small copper bar into the desired shape. The bracelet has a mass of 30.1 grams and was at a temperature of 21°C in the classroom. After the student wore the bracelet, the bracelet reached a temperature of 33°C. Later, the student removed the bracelet and placed it on a desk at home, where it cooled from 33°C to 19°C. The specific heat capacity of copper is 0.385 J/g•K.69 Explain, in terms of heat flow, the change in the temperature of the bracelet when the student wore the bracelet. [1]
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]
Answers
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.
Learn more:
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.
Related Questions
What is the total number of protons contained in the nucleus of a carbon 14 atom
The supercontinent that existed about 200 million years ago was named
Consider this molecular‑level representation of a mixture of gases. There are three gas particles containing two spheres. There are six gas particles containing a single sphere of a different color. There are five gas particles containing a single sphere of a third color. If the partial pressure of the diatomic gas is 0.330 atm, what is the total pressure?
What is 850 torr= ? Atm
Answers
Answer:
Both are right
Explanation:
A constant heat must be supplied for several minutes to soldering gun to overcome the melting point of solder. A butane torch is a type of soldering device powered (energised) by the burning of butane gas to melt and solder common metals
Answers
Answers
b. False
Answers
Answer: The given statement is true.
Explanation:
Incineration: It is a technique in which organic substance present in waste material is burned down to break them into its components.
For: Example : Burning of powder of wooden chips gives carbon dioxide gas ,nitrogen-dioxide in small amounts and heat energy.
Although incineration can break down harmful chemicals but the by-product formed are hazardous because:
- Oxides of nitrogen and sulfurs are also released which pollutes the air and becomes the main cause for acid rains.
- Green house gases are produced which disturbs the balance of atmosphere and climate.
- Increases air pollution by which it becomes unfit to breathe in.
- Also pollutes soil.
Hence, the given statement is true.
Answers
Answers
T₁ = 27.0ºC + 273 = 300 K
V₂ = ?
T₂ = 132.0 + 273 = 405 K
V₁ / T₁ = V₂ / T₂
900.0 / 300 = V₂ / 405
300 x V₂ = 405 x 900.0
300 x V₂ = 364500
V₂ = 364500 / 300
V₂ = 1215 mL
hope this helps!