Why are Group first elements called alkali metals?

The Group first elements are called alkali metals because they form water soluble hydroxides. Like LiOH, NaOH, KOH, RbOH and CsOH etc.

Why potassium carbonate cannot be prepared by Solvay process?

Potassium carbonate cannot be prepared by Solvay proces due to the reason that potassium bicarbonate (KHCO3) formed as an intermediate (When CO2 is Passed through ammoniated solution of potassium chloride) is highly soluble in water and can not be separated by filteration.

Which has more torsianal strain, butane or 2-methylbutane?

2-Methylbutane. It has two staggered conformer's with two Methyl group's adjacent to each other and one Methyl at a distance. The third staggered conformer has all three Methyl's adjacent to each other, and has the highest energy. Butane has only two Methyl groups to consider. There are two conformers with adjacent Methyl's, and one lowest energy conformer. the anti form.