11 P - Chemistry: Molecular Nature Of Matter And Change

Question

State whether each of the following substances is likely to be very soluble in water. Explain.

(a) Lithium nitrate 

(b) Glycine   $\left(H_2{\mathrm{NCH}}_2\mathrm{COOH}\right)$

(c) Pentane 

(d) Ethylene glycol $\left({\mathrm{HOCH}}_2{\mathrm{CH}}_2\mathrm{OH}\right)$

Step-by-Step Solution

Answer

(a) Lithium nitrate is soluble in water

(b) Glycine $\mathbf{\left(}{\mathbf{H}}_{\mathbf{2}}{\mathbf{NCH}}_{\mathbf{2}}\mathbf{COOH}\mathbf{\right)}$  is soluble in water

(c) Pentane is insoluble in water

(d) Ethylene glycol $\left({\mathrm{HOCH}}_2{\mathrm{CH}}_2\mathrm{OH}\right)$  is soluble in water

Determination of the solubility of Ionic compounds in water

The ionic compounds and the water molecules are polar in nature therefore both attract each other by the force of attraction.

Most ionic compounds dissociate and dissolve in water easily but if the force of attraction between ions of the ionic compound is stronger than the attraction force of water then its ionic bond does not dissociate and hence, these types of ionic compounds become water-insoluble.

Predict the solubility of lithium nitrate in water

Lithium nitrate is soluble in water because it is an ionic compound and polar in nature. It dissociates into ions on dissolving in water.

Determine the solubility of glycine in water

Glycine $\left({\mathrm{H}}_2{\mathrm{NCH}}_2\mathrm{COOH}\right)$  is soluble in water because it is a covalent compound and it contains polar hydrogen bonds in its molecular structure. Since water is also a polar molecule, it is soluble in water.

Determine the solubility of pentane in water

Pentane is insoluble in water because it is a non-polar compound since it does not contain any polar bonds in its structure. Hence it does not dissociate into ions in the presence of polar solvents.

Determine the solubility of ethyl glycol in water

Ethylene glycol $\left({\mathrm{HOCH}}_2{\mathrm{CH}}_2\mathrm{OH}\right)$   is soluble in water because it contains a polar $\text{O-H}$ bond. As the molecule is itself polar it dissolves in polar solvents like water.