You are attempting to determine the thermodynamic properties of an unknown compound. You’ve already determined delta H fusion to be 5.56 kJ/mol and delta H vaporization to be 21.99 kJ/mol. In one of these previous experiments, 2.56 g of this compound was placed in a glass bulb and vaporized by placing the glass bulb into 200. g of hot water initially at 68.25 degrees Celsius, which resulted in a final water temperature of 67.91 degrees Celsius. You are now attempting to determine the enthalpy of solution of this compound. To this end, you dissolve 55.6 g of this compound in 495 g of water initially at 25.2 degrees Celsius. The final temperature of the solution is 19.4 degrees Celsius. What is the enthalpy of solution of this compound in kJ/mol?

The heat of solution of the compound = 42.75 kJ/mol

Explanation:

Here we have;

The heat of vaporization = 21.99 kJ/mol

2.56 g of the compound is then placed in 200 g. of water

The temperature of the water reduces from 68.25°C to 67.91°C

The specific heat capacity of water = 4.19 kJ/kg = 4.19 J/g

Mass of the water = 200 g

Heat lost by the water ΔH = m × c × Δθ = n × ΔH vaporization of the compound

Where;

m = The mass of the water = 200 g

c = The specific heat capacity of water = 4.19 kJ/kg = 4.19 J/g

Δθ = The change in temperature = 68.25°C - 67.91°C = 0.34°C

n = The number of moles of the compound

ΔH = m × c × Δθ = 200×4.19×0.34 = 284.92 J = 0.28492 kJ

∴ n × ΔH vaporization of the compound = 0.28492 kJ

n = 0.28492 kJ/( ΔH vaporization of the compound) = 0.28492/21.99≈0.013 moles

∴ 2.56 g = 0.013 moles

1 mole = The molar mass of the compound = 2.56/0.013= 197.6 g/mol

Therefore;

The number of moles in 55.6 g of the compound = 55.6/197.6 = 0.2814 moles

The heat given by the water = ΔH = 495 × (25.2 - 19.4) × 4.19 = 12029.49 J

Therefore;

0.2814 × ΔH(solution) = 12029.49 J = 12.02949 kJ

ΔH(solution) = 12.02949/0.2814 = 42.75 kJ/mol

The heat of solution of the compound = 42.75 kJ/mol.

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.