Answer:
Al 72.61%
Mg 27.39%
Explanation:
To obtain the mass percentages, we need to place the individual masses over the total mass and multiply by 100%.
If we observe clearly, we can see that the parameters given are the moles. We need to convert the moles to mass.
To do this ,we need to multiply the moles by the atomic masses. The atomic mass of aluminum is 27 while that of magnesium is 24.
Now, the mass of aluminum is thus = 27 * 0.0898 = 2.4246g
The mass of magnesium is 0.0381 * 24 = 0.9144g
We can now calculate the mass percentage.
The total mass is 0.9144 + 2.4246 = 3.339g
% mass of Al = 2.4246/3.339 * 100 = 72.61%
% mass of Mg = 0.9144/3.39 * 100 = 27.39%
Answer:
premium: 91 octane rating
Explanation:
Octane number refers to the percentage or volume fraction of isooctane in a fuel.
The octane number gives a picture of how safe a fuel is for an engine. The higher the octane rating the lesser the tendency of the fuel to cause knocking of the engine.
The type of gasoline with the highest percentage of octane among the options is premium.
Answer:
Explanation:
The following equation relates to Born-Haber cycle
Where
is enthalpy of formation
S is enthalpy of sublimation
B is bond enthalpy
is ionisation enthalpy of metal
is electron affinity of non metal atom
is lattice energy
Substituting the given values we have
-435.7 = 79.2 + 1/2 x 242.8 + 418.7 - 348 +U_L
= - 707 KJ / mol
Answer:
A) ∆Suniv >0, ∆G<0, T∆Suniv >0.
Explanation:
The connection between entropy and the spontaneity of a reaction is expressed by the <u>second law of thermodynamics</u><u>: The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process</u>.
Mathematically, we can express the second law of thermodynamics as follows:
For a spontaneous process: ΔSuniv = ΔSsys + ΔSsurr > 0
Therefore, the second law of thermodynamics tells us that a spontaneous reaction increases the entropy of the universe; that is, ΔSuniv > 0.
If we want spontaneity expressed only in terms of the properties of the system (ΔHsys and ΔSsys), we use the following equation:
-TΔSuniv = ΔHsys - TΔSsys < 0
That means that T∆Suniv >0.
This equation says that for a process carried out at constant pressure and temperature T, if the changes in enthalpy and entropy of the system are such that <u>ΔHsys - TΔSsys is less than zero, the process must be spontaneous.</u>
Finally, if the change in free energy is less than zero (ΔG<0), the reaction is spontaneous in the forward direction.
Explanation:
Using the expression :
Where, 
is the dissociation constant of water.
At 
, 
Thus, for HCN , 
<u>
for CN⁻ can be calculated as:</u>
Thus, for NH₃ , 
<u>
for 
can be calculated as:</u>
