<u>Answer</u>:
A solid will melt at the temperature at which the kinetic energy breaks the
inter-molecular attractions.
<u>Explanation</u>:
The melting point is the state at which "a substance changes its temperature from a solid to liquid". At the melting point temperature, there is an equilibrium between the both the solid and the liquid phase. When the solid particle is heated by increasing the temperature the particle in the solid vibrate quickly and it absorbs kinetic energy.
It leads to the breaking of the organisation of particle in between the solid and that leads to the melting of solid. Thus, at the melting point, the kinetic energy breaks the inter-molecular attractions.
The mass of 165.0 g sample that remains after 90.0 minutes is 5.16 grams
calculation
lambda㏑2/18= 0.0385
m(t)= 165 x e( 0.0385 x90) =5.16g
The effective nuclear charge is the net positive charge experienced by valence electrons
