The diagram above represents the melting of H2O(s). A 2.00mole sample of H2O(s) at 0°C melted, producing H2O(l) at 0°C. Based on the diagram, which of the following best describes the amount of heat required for this process and the changes that took place at the molecular level?

Heat : 12 kJ,  to maintain hydrogen bonds

Given

A 2.00mole sample ⇒ n = 2 mol

H₂O(s) at 0°C melted, producing H₂O(l) at 0°C

Required

the amount of heat required

the changes that took place

Analysis

Conversion of mol to mass

Use formula of Heat  :

Q = mLf (melting/freezing)  

Lf=latent heat of fusion  (for water=334 J/g)

Solution

mass H₂O(MW=18 g/mol) :

Heat required :

The absorbed heat is used to maintain hydrogen bonds in water molecules (there are two hydrogen bonds per molecule)

Paraphrase

The amount of heat required : 12 kJ, and to maintain hydrogen bonds

5.0 M NaCl

Explanation:

A concentrated solution is one which has more amount of solute in it.

A dilute solution is one which has less amount of solute in it.

Molarity is defined as the number of moles of solute present per liter of the solution.

0.5 M NaCl will have 0.5 moles of NaCl in 1 L of the solution, 0.005 M NaCl has 0.005 moles of NaCl in 1 L of the solution, 0.05 M NaCl has 0.05 moles of NaCl in 1 L and 5.0 M NaCl has 5 moles of NaCl in 1 L.

Thus 5.0 M NaCl will be most concentrated.