Question

For each of the following solute-solvent combinations state the sign and relative magnitude of $\mathbf{∆}{\mathbf{H}}_{\mathbf{1}}$, $\mathbf{∆}{\mathbf{H}}_{\mathbf{2}}$, $\mathbf{∆}{\mathbf{H}}_{\mathbf{3}}$, $\mathbf{∆}{\mathbf{H}}_{\mathbf{sol}}$(as defined in figure 17.1 of text). Explain your answer.

Short answer

Examples	State of solute	State of solvent	State of solution
Acetone and water	liquid	liquid	liquid
Ethanol and water	liquid	liquid	liquid
Heptane and hexane	Liquid	liquid	liquid
Heptane and water	liquid	liquid	Does not form a solution.

The value of $∆{\mathrm{H}}_1,∆{\mathrm{H}}_2,∆{\mathrm{H}}_3,∆{\mathrm{H}}_{\mathrm{sol}}$following parts are as follows

Step-by-step solution

Step 1- Acetone and water

(a)

$∆{\mathrm{H}}_1$= large, positive value

localid="1663784712744" $∆{\mathrm{H}}_2$=large, positive value

$∆{\mathrm{H}}_3$= large, negative value

$∆{\mathrm{H}}_{\mathrm{sol}}$= small positive value

In the first part there is a mixture of acetone and water, and both the molecules are polar molecules as they have a polar bond. So, the property of polar solute and the polar solvent solution will be applied.

Step 2- Ethanol and water

(b)

$∆{\mathrm{H}}_1$= large, positive value

localid="1663784724125" $∆{\mathrm{H}}_2$= large, positive value

$∆{\mathrm{H}}_3$= large, negative value

$∆{\mathrm{H}}_{\mathrm{sol}}$= small positive value

In the second part there is a mixture if ethanol and water and both the molecules are polar molecules as they have polar bonds. So they will have properties of polar solute and polar solvent.

Step 3- Heptane and hexane

(c)

$∆{\mathrm{H}}_1$= small, positive value

$∆{\mathrm{H}}_2$= small , positive value

$∆{\mathrm{H}}_3$= small e, negative value

$∆{\mathrm{H}}_{\mathrm{sol}}$= small, positive value

In the third part, we have a mixture of heptane and hexane both are non-polar solute and solvent so they will dissolve and form a solution that shows the properties of the non-polar solute and non-polar solvent.

Step 4- Heptane and water

(d)

$∆{\mathrm{H}}_1$= small, positive value

$∆{\mathrm{H}}_2$= large, positive value

$∆{\mathrm{H}}_3$= small, positive value

$∆{\mathrm{H}}_{\mathrm{sol}}$= large, positive value

In this mixture, we have heptane as a solute which is non-polar, and water as a solvent which is polar so this mixture will show the property of non-polar solute and polar solvent mixture. Also, this combination will not form any solution as the solute and solvent are not of the same type i.e one is non-polar, and one is polar.