What is the freezing point of a solution of 1.43 g mgcl2 in 100 g of water? Kf for water is 1.86°c/m for water.

Change in T = i x m x kf. Where i is the number of particles the compound dissociates, m is the molality, and kf is the constant specific to water.  MM of MgCl2 = 95.21 g/mol

MgCl2 will form three atomsi = 31Mg + 2Cl

kf = 1.86

moles of MgCl2 = 1.43g/95.21 = 0.015

m = moles solute/ kg solvent = 0.015/.1kg = .15m

Change in T = (3)(.15)(1.86) = .838

This is the depression of the freezing point of water, it is negative because the water's new freezing point is its normal freezing point minus the change in T.

0 - .838 = -.838

Explanation:

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3