Why is `Li_2CO_3` decomposed at a lower temperature where as `Na_2CO_3` does not?

Why Li_2CO_3 decomposes at lower temperature whereas Na_2CO_3 at higher temperature?

Li_2CO_3 decomposes at a lower temperature whereas Na_2CO_3 at higher temperature.why?

State as to why a solution of Na_2CO_3 is alkaline

Solvay process is used for the manufacture of NaOH' 'Na_2 CO_3' NH_3' NaCl'

10 dm^3 of N_2 gas and 10 dm^3 of gas x at the same temperature contain the same number of molecules. The gas x is CO , CO_2 , H_2 , NO