Answer: 4.18925 kJ heat is needed to convert 25.0 g of solid ethanol at -135 °C to liquid ethanol at -50°C.
Explanation:
Temperature of Solid
Melting temperature of Solid
Temperature of liquid
Specific heats of solid ethanol = 0.97 J/gK
Specific heats of liquid ethanol = 2.3 J/gK
Heat required to melt the the 25 g solid at 159 K
= 159 K - 138 K = 21 K
Heat required to melt and raise the temperature of upto 223 K
= 223 K - 159 K = 64 K
Total heat to convert solid ethanol to liquid ethanol at given temperature :
(1kJ=1000J)
Hence, 4.18925 kJ of heat will be required to convert 25.0 g of solid ethanol at -135 °C to liquid ethanol at -50°C.
Answer:
Option C. 52.057
Explanation:
The following data were obtained from the question:
Isotope >> Mass number > Percentage
A (Cr-50) > 50 >>>>>>>>>> 4.3
B (Cr-52) > 52 >>>>>>>>>> 83.8
C (Cr-53) > 53 >>>>>>>>>> 9.5
D (Cr-54) > 54 >>>>>>>>>> 2.4
Average atomic mass =?
The average atomic mass of chromium, Cr can be obtained as follow:
Average atomic mass = [(Mass of A × A%) /100] + [(Mass of B × B%) /100] + [(Mass of C × C%) /100] + [(Mass of D × D%) /100]
Atomic mass of Cr = [50×4.3)/100] + [52×83.8)/100] + [53×9.5)/100] + [54×2.4)/100]
= 2.15 + 43.576 + 5.035 + 1.296
Atomic mass of Cr = 52.057
Therefore, the atomic mass of chromium, Cr is 52.057
Answer:
The 1st law of thermodynamics and the 2nd law of themodynamics
Explanation:
The first law of thermodynamics describes the conservation of energy. It states that when heat is added to a system, it transforms to an equal amount of another form of energy. It does this by doing one or both of the following things: (1) increasing the amount of internal energy within the system; and/or (2) doing external work by leaving the system, thereby affecting the area around the system.
The second law of thermodynamics states that no reaction is completely efficient and that heat is always transferred from warmer objects to colder objects. In other words, some energy is always lost to heat in any reaction, and you'll never find heat moving from colder objects to warmer objects in a system
The mass, in grams, of NaCl needed to use to make the solution is 1.76grams.
<h3>HOW TO CALCULATE MASS?</h3>
The mass of a substance can be calculated by multiplying the number of moles by its molar mass.
However, the number of moles must first be calculated by using the following expression:
Molarity = no. of moles ÷ volume
no. of moles = 0.249 × 0.1208
no. of moles = 0.03moles
Molar mass of NaCl = 23 + 35.5 = 58.5g/mol
mass of NaCl = 0.03 × 58.5 = 1.76g
Therefore, the mass, in grams, of NaCl needed to use to make the solution is 1.76grams.
Learn more about mass at: brainly.com/question/19694949
a. energy is released
Explanation:
When a nitrogen molecule forms, energy is usually released. During a bond formation process, energy is usually released.
- In a bond dissociation process, energy is usually absorbed to break bonds.
- But when bonds are forming, energy is usually released.
- Bond formation is an exothermic change in which heat energy is released into the environment.
- Bond dissociation is an endothermic change.
Learn more:
Enthalpy changes brainly.com/question/10567109
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