Soutions are made that contain 0.1 moles of each of the following compunds below in 100 of H2O. Choose the compounds whose solutions will have the lowest freezing point.
A)MgCl2
B)MgSO4
C)KClO3
D)CO2
E)NaBr
100 WHAT of H2O?? grams? That's 0.1 kg.
Use delta T = i*Kf*m
where i is the van't Hoff factor (the number of particles in solution). m is the same, Kf is the same, the only thing changing is i. You CAN do it the long way and calculate each BUT you can look at it and know which is the larger delta T by inspection.
To determine which compound will have the lowest freezing point, we need to compare the number of particles (i.e., ions or molecules) that are formed when each compound dissolves in water.
A) MgCl2:
When MgCl2 dissolves in water, it dissociates into Mg2+ and 2 Cl- ions. So, in 0.1 moles of MgCl2, there will be 0.1 moles of Mg2+ ions and 0.2 moles of Cl- ions. Therefore, the total number of particles is 0.1 + 0.2 = 0.3 moles.
B) MgSO4:
When MgSO4 dissolves in water, it dissociates into Mg2+ and SO42- ions. So, in 0.1 moles of MgSO4, there will be 0.1 moles of Mg2+ ions and 0.1 moles of SO42- ions. Therefore, the total number of particles is 0.1 + 0.1 = 0.2 moles.
C) KClO3:
KClO3 does not dissociate into ions when dissolved in water. Therefore, it will remain as individual molecules. So, in 0.1 moles of KClO3, there will still be 0.1 moles of KClO3 molecules. Therefore, the total number of particles is 0.1 moles.
D) CO2:
CO2 does not dissociate into ions when dissolved in water. Therefore, it will remain as individual molecules. So, in 0.1 moles of CO2, there will still be 0.1 moles of CO2 molecules. Therefore, the total number of particles is 0.1 moles.
E) NaBr:
When NaBr dissolves in water, it dissociates into Na+ and Br- ions. So, in 0.1 moles of NaBr, there will be 0.1 moles of Na+ ions and 0.1 moles of Br- ions. Therefore, the total number of particles is 0.1 + 0.1 = 0.2 moles.
To find the compound with the lowest freezing point, we need to consider the number of particles in each solution. The more particles present in a solution, the lower its freezing point. Comparing the total number of particles in each compound's solution, we find that KClO3 has the lowest number of particles (0.1 moles). Therefore, the solution of KClO3 will have the lowest freezing point among the given compounds.