The mass percentage of bismuth in the compound will be equal to the mass of bismuth in one mole of compound divided by the total molar mass of the compound.

Bismuth has a molar mass of $\displaystyle 208.98\frac{g}{mol}$. One mole of the compound would result in two moles of bismuth, a total of 417.96g.

$\displaystyle 2(208.98)=417.96g$

Tellurium has a molar mass of $\displaystyle 127.6\frac{g}{mol}$. One mole of the compound would result in three moles of tellurium, a total of 382.8g.

$\displaystyle 3(127.6)=382.8g$

Add the mass of bismuth and the mass of tellurium per mole to find the total molar mass.

$\displaystyle MM=417.96g+382.8g=800.76g$

Divide the mass of bismuth by the total molecular mass to find the percent by mass of bismuth in the compound.

$\displaystyle \frac{417.96g}{800.76g}\times100\%=52.2\%$

The total molar mass of acetic acid is $\displaystyle 60\frac{g}{mol}$.

$\displaystyle 2(12)+2(16)+4(1)=60\frac{g}{mol}$

Carbon contributes $\displaystyle 24g$ total. Therefore, in a sample of 1 mole of acetic acid, there are $\displaystyle 24g$ of carbon. To find the percent by mass, we must divide the mass of carbon by the total molar mass of the compound.

$\displaystyle \frac{24g}{60g}=40\%$

The total molar mass of lead (II) sulfate is $\displaystyle 303.265g/mol$. Lead contributes $\displaystyle 207.2g$, sulfur contributes $\displaystyle 32.065g$, and oxygen contributes $\displaystyle (4*16g)=64g$.

The percent by mass of each element in the compound is found by dividing the mass contribution of that element by the total molar mass of the compound.

$\displaystyle Pb: \frac{207.2gPb}{303.265gtotal}=68.33\%$

$\displaystyle S: \frac{32.065gS}{303.265gtotal}=10.57\%$

$\displaystyle O: \frac{64gO}{303.265gtotal}=21.1\%$

The molar mass of calcium chloride is $\displaystyle 110.987\frac{g}{mol}$. Chlorine has two moles per one mole of $\displaystyle CaCl_{2}}$. Therefore, chloride contributes 70.9g to the total molecular mass.

$\displaystyle (2mol*35.45\frac{g}{mol})=70.9g$

To find the percent by mass of chlorine in calcium chloride, divide the contribution of chlorine by the total molar mass.

$\displaystyle \frac{70.9g}{110.987g}=63.9\%$

The total mass of one mole of aluminum (II) chromate is calculated by:

$\displaystyle 2(26.98\frac{g}{mol} Al)+3(51.99\frac{g}{mol} Cr)+12(16\frac{g}{mol}O)=401.95\frac{g}{mol}Al_2(CrO_4)_3$

Aluminum, chromate, and oxygen contribute $\displaystyle 53.96g, 155.97g,$ and $\displaystyle 192g$respectively. Therefore, we can divide each contribution by the total molecular mass to determine percentages by mass.

$\displaystyle Al: \frac{53.96gAl}{401.95gtotal}=13.42\%$

$\displaystyle Cr: \frac{155.97gCr}{401.95gtotal}=38.8\%$

$\displaystyle O: \frac{192gO}{401.95gtotal}=47.78\%$

The total mass of $\displaystyle U(C_{2}H_{3}O_{2})_{3}$ is $\displaystyle 415.16\frac{g}{mol}$ and calculated by:

$\displaystyle (238.0289\frac{g}{mol}U)+6(12.01\frac{g}{mol}C)+9(1.008\frac{g}{mol}H)+6(16\frac{g}{mol}O)=415.16\frac{g}{mol}U(C_2H_3O_2)_3$

You can then divide hydrogen's contribution by the total molecular mass in order to find the percent mass.

$\displaystyle \frac{9.072g}{415.16g}=2.18\%$

The total molar mass of $\displaystyle Cs_{2}Se$ is $\displaystyle 344.78\frac{g}{mol}$. Cesium has a +1 charge when the compound is dissolved in solution and is, thus, the cation.

$\displaystyle Ce_2Se\rightarrow2Ce^{+1}+Se^{-2}$

Cesium contributes 265.8g to the total molecular mass.

$\displaystyle (2mol*132.9\frac{g}{mol}Cs)=265.8gCs$

We can find the percent by mass of cesium by dividing the mass of cesium by the total molecular mass.

$\displaystyle \frac{265.8gCs}{344.78g\ total}=77.1\%$

A hydrogen bond is not a proper chemical bond, but the result of dipole-dipole interactions. While they are very chemically important, hydrogen bonds are dynamic, rather than stagnant. This is the least stable type of bond listed.

Covalent bonds are inherently more stable than ionic bonds as electrons are shared between both bound atoms, so the next stronges bond type is the ionic bond.

Chemists distinguish between covalent and ionic bonds for the sake of simplicity, but there is actually a continuum. Polar covalent bonds are on the continuum between pure ionic bonds and pure covalent bonds, so polar covalent bonds have more ionic character than nonpolar covalent bonds, and thus are less stable than nonpolar covalent bonds.

IMF strength is in the order of ion-ion>h-bond>dipole-dipole>van der waals. Of the listed compounds there aren't any that display ion-ion IMF, and only ammonia has h-bonding, making it the one with the strongest forces.

Helium gas will have the lowest boiling point since it is a noble gas and the only intermolecular forces present are dispersion forces, which are the weakest. Acetone has a dipole, so dipole-dipole forces will be present. Water has a dipole and can also hydrogen bond, as can isobutyl alcohol. However, isobutyl alcohol is heavier than water, and will thus have the highest boiling point.