Question

1. predict the approximate ph (ph = 7, ph > 7 or ph < 7) of fairly concentrated aqueous solutions of the following compounds from model 2. lactic acid amino acid dopamine lactose

Explanation:

Step1: Identify acid - base nature

Lactic acid is an organic acid. In aqueous solution, it dissociates to release H⁺ ions, making the solution acidic. So pH < 7.

Step2: Consider amino - acid behavior

Amino - acids have both acidic (carboxyl group) and basic (amino group) functional groups. In a fairly concentrated aqueous solution, their net behavior depends on the pKa values of the functional groups. However, in general, they can act as acids and the solution is likely to have pH < 7.

Step3: Analyze dopamine

Dopamine has a basic amine group and can accept H⁺ ions in solution. But in a fairly concentrated aqueous solution, the presence of water - autoionization and the overall balance of species leads to a slightly basic solution, pH > 7.

Step4: Evaluate lactose

Lactose is a disaccharide and is a neutral compound. It does not significantly affect the concentration of H⁺ or OH⁻ ions in water. So the solution of lactose has pH = 7.

Answer:

Lactic acid: pH < 7
Amino acid: pH < 7
Dopamine: pH > 7
Lactose: pH = 7