7.20594 x 10^20
First you must determine how many moles of P3O5 you have. This is done by using the formula
Number of moles (n) = mass in grams of substance (m) /divided by/ Molar mass (M) [this is the sum of the atomic mass of all atoms in the compound]
n = 0.170 / P (31 x 2) + O (16 x 5)
n = 0.170 / 142
n = 0.001197 moles
Then you use avagadros number 6.02 x10^23 this is the number of atoms in one mole of any substance. Since you have 0.001197 moles you multiply the number of moles by avagadros number
0.001197 x (6.02 x 10^23)
= 7.20594 x 10^20 atoms
Colligative properties calculations are used for this type of problem. Calculations are as follows:
ΔT(boiling point) = 101.02 °C - 100.0 °C= 1.02 °C
<span>ΔT(boiling point) = (Kb)m
</span>m = 1.02 °C / 0.512 °C kg / mol
<span>m = 1.99 mol / kg
</span><span>ΔT(freezing point) = (Kf)m
</span>ΔT(freezing point) = 1.86 °C kg / mol (<span>1.99 mol / kg)
</span>ΔT(freezing point) = 3.70 <span>°C
</span>Tf - T = 3.70 <span>°C
T = -3.70 </span><span>°C</span>
