Answer:
3.24 × 10^5 J/mol
Explanation:
The activation energy of this reaction can be calculated using the equation:
ln(k2/k1) = Ea/R x (1/T1 - 1/T2)
Where; Ea = the activation energy (J/mol)
R = the ideal gas constant = 8.3145 J/Kmol
T1 and T2 = absolute temperatures (K)
k1 and k2 = the reaction rate constants at respective temperature
First, we need to convert the temperatures in °C to K
T(K) = T(°C) + 273.15
T1 = 325°C + 273.15
T1 = 598.15K
T2 = 407°C + 273.15
T2 = 680.15K
Since, k1= 8.58 x 10-9 L/mol, k2= 2.16 x 10-5 L/mol, R= 8.3145 J/Kmol, we can now find Ea
ln(k2/k1) = Ea/R x (1/T1 - 1/T2)
ln(2.16 x 10-5/8.58 x 10-9) = Ea/8.3145 × (1/598.15 - 1/680.15)
ln(2517.4) = Ea/8.3145 × 2.01 × 10^-4
7.831 = Ea(2.417 × 10^-5)
Ea = 3.24 × 10^5 J/mol
Answer:
737.52 mL de agua
Explanation:
En este caso solo debes usar la expresión de molaridad de una solución la cual es:
M = moles / V
Donde:
V: Volumen de solución.
Como queremos saber la cantidad de agua, queremos saber en otras palabras cual es la cantidad de solvente que se utilizó para preparar los 800 mL de disolución.
Una disolución se prepara con un soluto y solvente. El soluto lo tenemos, que es el nitrato de plata. Con la expresión de arriba, calculamos los moles de soluto, y luego su masa. Posteriormente, calculamos el volumen con la densidad, y finalmente podremos calcular el solvente de esta forma:
V ste = Vsol - Vsto
Primero calcularemos los moles de soluto:
moles = M * V
moles = 2 * 0.800 = 1.6 moles
Con estos moles, se calcula la masa usando el peso molecular reportado que es 169.87 g/mol:
m = moles * PM
m = 1.6 * 169.87 = 271.792 g
Ahora usando el valor de la densidad, calcularemos el volumen de soluto empleado:
d = m/V
V = m/d
V = 271.792 / 4.35
V = 62.48 mL
Finalmente, la cantidad de agua necesaria es:
V agua = 800 - 62.48
V agua = 737.52 mL
Heat given out to the surroundings by the system = 225 J
Work done by the system on the surroundings = 645 J
According to the energy conservation, the energy can neither be created nor it can be destroyed, it can transform from one form to another. Hence, the energy which is lost to the surrounding as a work done and heat came from the internal energy of the system.
Hence, the change in the internal energy = - 225 - 645 = - 870 Joules
Negative sign means that the internal energy of the system is decreased by 870 Joules
<span>2.59 g/cm^3
For a face centered cubic crystal, there is 1 atom at each corner that's shared between 8 unit cells. And since there's 8 corners, that gives 8*1/8 = 1 atom per unit cell. Additionally, there are 6 faces, each with 1 atom, that's shared between 2 cells. So 6*1/2 = 3. So each unit cell has a mass of 1 + 3 = 4 atoms. The size of the unit cell will be equal to either the diameter of one atom along the edge, or the diameter of 2 atoms as the diagonal across one face of the cube, whichever results in the larger unit cell. Taking that into consideration, I will use the value of 2 for the diagonal of a face of the unit cell, resulting in the length of an edge of the unit cell being sqrt(2^2/2) = sqrt(2) = 1.414213562 times the atomic diameter. So
1.414213562 * 2 * 0.215 nm = 0.608 nm
So the volume of a single unit cell is (0.608 nm)^3
Avogadro's number of atoms will require 6.0221409x10^23 / 4 = 1.50554x10^23 unit cells and will have a mass of 87.62 grams. The volume will be
1.50554x10^23 * (0.608x10^-7 cm)^3
= 1.50554x10^23 * 0.224755712x10^-22 cm^3
= 33.83776414 cm^3
So the density is approximately 87.62 g/33.83776414 cm^3 = 2.589414585 g/cm^3, when rounded to 3 significant figures is 2.59 g/cm^3.</span>
