CH4 (g) + 2Cl2 (g) --> CH2Cl2 (g) + 2HCl (g) <span>ΔH = -205.4</span>
Answer:
A and C are true , B and D are false
Explanation:
For A)
from the first law of thermodynamics (in differential form)
dU= δQ - δW = δQ - PdV
from the second law
dS ≥ δQ/T
then
dU ≤ T*dS - p*dV
dU - T*dS + p*dV ≤ 0
from the definition of Gibbs free energy
G=H - TS = U+ PV - TS → dG= dU + p*dV + V*dp - T*dS - S*dT
dG - V*dp + S*dT = dU - T*dS + p*dV ≤ 0
dG ≤ V*dp - S*dT
in equilibrium, pressure and temperature remains constant ( dp=0 and dT=0). Thus
dG ≤ 0
ΔG ≤ 0
therefore the gibbs free energy should decrease in an spontaneous process → A reaction with a negative Gibbs standard free energy is thermodynamically spontaneous under standard conditions
For B) Since the standard reduction potential is related with the Gibbs standard free energy through:
ΔG⁰=-n*F*E⁰
then, when ΔG⁰ is negative , E⁰ is positive and therefore a coupled redox reaction with a positive standard reduction potential is thermodynamically spontaneous.
Answer:
The true statement about the discovery of electrons is :
C. Electrons were discovered in a vacuum tube
Explanation:
In 1870, Sir William Crookes developed the first cathode ray tube which have high vacuum inside.
These rays moved the paddled wheel when placed in their path.This means these rays have some momentum.
When the magnetic field was applied to the cathode rays they showed deflection. This means these cathode rays must have some charge because only charged particles can show deflection when place in magnetic field.
Later is was found by J.J Thomson that these are negatively charged.
How ?
We Know that like charges repel each other and unlike charges attract each other. This means if a particle has negative charge then it will attract the positive charge.
J.J Thomson studied these cathode ray tubes and found that these rays repels the negative charge particles .Hence these rays must be negatively charged.
He called these tiny Particle "electron"
Answer: 20 I think
Explanation:
1 in each corner, 3 across from it. 3x4=12 plus one next to each is 20