Choose and explain: a. Strongest base to H (gas phase): NH3, CH3NH2, (CH3)2NH, (CH3)3N
b. Strongest base to BMe3: pyridine,
2-methylpyridine, 4-methylpyridine

a) (CH3)3N

b) 4-methylpyridine

Explanation:

Let us bear in mind that the basicity of amines depend on;

1) the availability of the lone pair

2) the stability of the conjugate acid of the amine.

In the gaseous phase, the basicity of the amine strictly depends on the availability of the lone pair. The tertiary amine is better able to accept a proton in the gaseous phase since it is surrounded by three methyl groups having an electron pushing effect thereby reinforcing the lone pair on the nitrogen. This order is reversed in solution due to solvation.

Here again, the electron donation to the nitrogen bearing the lone pair is important. The 4-methylpyridine is more basic than 2-methylpyridine to BMe3 due to steric hindrance that hinders the bonding of 2-methylpyridine to BMe3.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.