Question

1. Which is a more closely packed crystal?

	A) A crystal where each atom has 6 nearest neighbors
	B) A crystal where each atom has 8 nearest neighbors
	C) A crystal where there is only 1 total atom per unit cell.

2. What causes freezing point temperature lowering or what is called freezing point depression?

	A) removing solute from a solution
	B) adding solute to a solution
	C) changing the temperature

Answer 1

1.A. A crystal wheree atom has 6 nearest neighbours that means the atom is actually in an octahedral site. This type of arrangement is obtained where one type of atoms or ions are arranged in cubic close packing(ccp) arrangement and the other atoms occupy the octahedral sites.... example- NaCl (that is

In each unit cell of sodium chloride there are 4 Na⁺ ions and 4Cl^- ions ..(total 8 ions per unit cell)

That is total 4 NaCl per unit cell....

B. A crystal where each atom has 8 nearest neighbours means that one type of atom or ions are in a simple cubic arrangement and other type of atoms or ions occupy the cubic interstitial site.....[one atom in the middle of the unit cell which is surrounded by eight other type of atoms posited in the eight corners of the unit cell each contributing 1/8 to the unit cell...that is total [1+(8×1/8)]=2 atoms or ions per unit cell....

Example-CsCl...

There are 1 molecule of CsCl (that is one Cs⁺ and one Cl^{​​​​​-}​​​​ , total 2 ions) per unit cell...

3. Only one atom per unit cell

from the above discussion we can easily conclude that

A) A crystal where each atom has 6 nearest members is the most closely packed crystal....(ANSWER)

2. DEPRESSION OF FREEZING POINT is a colligative property that is it completely depends on the number of solute molecules atoms or ions dissolved in in the solvent....

Hence we can conclude that the cause of freezing point temperature lowering is B) adding solute to a solution.....(ANSWER)....