Question

For each solute, identify the better solvent water or carbon tetrachloride.

HOW CAN I TELL please be detailed

Answer 1

Ans. Part A: Water

Water is a polar solvent. It dissolves polar and ionic molecules.

NH₃ is a polar molecule because of having a net dipole moment. It’s central N-atom has a partial negative charge and the H-atoms are partially passively charged. Negatively charged N-atom of ammonia interacts with (form Hydrogen bonds) H-atoms of water that bear partial positive charge. Similarly, the partial positive charge bearing H-atoms of ammonia form H-bonds with O-atoms of water. Thus, because of owing polarity, NH3 dissolves in water through formation of H-bonds.

Potassium fluoride is an ionic compound. When in contact with water, positively charged K⁺ ions are surrounded by several O-atoms of water molecules and hydrated or solvated. Similarly, the negatively charged F^- ions are solvated by several H-atoms of water molecule that bear partial positive charge. Therefore, in water solvent, the resultant ions of KF are hydrated resulting KF to dissolve.

Part B: Carbon tetrachloride is a non-polar molecule. It dissolves non-polar solutes in it.

I₂: Two iodine atoms linked together by covalent bond in a diatomic iodine (I₂) results a net dipole of 0 (zero) because both the atoms have the same electronegativity. Therefore, I₂ behaves much like a non-polar solvent. It is better solvated in non-polar solvent following “like dissolves like” because both the non-polar solvent and solute molecules interact among each other with weak van der Wall’s forces of attraction.

C6H6 is also non-polar like CCl4. Thus, it is soluble in CCl4. [see I2 solubility].