The items are answered below and are numbered separately for each compound.
The freezing point of impure solution is calculated through the equation,
Tf = Tfw - (Kf)(m)
where Tf is the freezing point, Tfw is the freezing point of water, Kf is the freezing point constant and m is the molality. For water, Kf is equal to 1.86°C/m. In this regard, it is assumed that m as the unit of 0.25 is molarity.
1. NH4NO3
Tf = 0°C - (1.86°C/m)(0.25 M)(2) = -0.93°C
2. NiCl3
Tf = 0°C - (1.86°C/m)(0.25 M)(4) = -1.86°C
3. Al2(SO4)3
Tf = 0°C - (1.86 °C/m)(0.25 M)(5) = -2.325°C
For boiling points,
Tb = Tbw + (Kb)(m)
For water, Kb is equal to 0.51°C/m.
1. NH4NO3
Tb = 100°C + (0.51°C/m)(0.25 M)(2) = 100.255°C
2. NiCl3
Tb = 100°C + (0.51°C/m)(0.25 M)(4) = 100.51°C
3. Al2(SO4)3
Tb = 100°C + (0.51°C/m)(0.25 M)(5) = 100.6375°C
I believe it would be compound.
Here's my best guess
the volume of the unit cell is (385*10^-12)^3=5.7066*10^-29 m^3
multiply by density to get mass
mass = (7 g/cm^3)*(100^3 cm^3 / 1^3 m^3) * 5.7066*10^-29 m^3= 3.99466*10^-22 g
covert to moles
3.99466*10^-22 g * 1 mol / 239.82 g = 1.6657 *10^-24 mol
convert to number of units
1.6657 *10^-24 mol * 6.23*10^23 units/mol = 1.04
385 pm = 3.85*10^(-8) cm
The volume of the unit cell is the cube of that, which is 5.71*10^(-23) cm^3. Since the ratio of mass to volume (i.e. the density) must be the same no matter what amount of TlCl you have, you can say:
7 = x/(5.71*10^(-23)), where x is the mass of the unit cell. Solving for x, you get 4*10^(-22) g.
The mass of a molecule of TlCl is 240 amu, which in grams is 4*10^(-22) g. The mass of the unit cell and the mass of a molecule of TlCl is the same. Therefore there is one formula unit of TlCl per unit cell.
Answer: Most of the stars in the universe are main sequence stars — those converting hydrogen into helium via nuclear fusion. A main sequence star may have a mass between a third to eight times that of the sun and eventually burn through the hydrogen in its core. Over its life, the outward pressure of fusion has balanced against the inward pressure of gravity. Once the fusion stops, gravity takes the lead and compresses the star smaller and tighter.
Temperatures increase with the contraction, eventually reaching levels where helium is able to fuse into carbon. Depending on the mass of the star, the helium burning might be gradual or might begin with an explosive flash.
