To determine the percent of LiHCO3 in the mixture, we need to calculate for the amount of LiHCO3 by first knowing what really happens in the process. We do as follows:
2 LiHCO3(s) --Heat--> Li2CO3(s) + H2CO3(g)
0.275 g = mass of H2CO3
mass of LiHCO3 = 0.275g (1 mol / 62.03 g) ( 2 mol LiHCO3 / 1 mol H2CO3 ) (67.96 g / 1 mol ) = 0.6026 g LiHCO3
% percent = 0.6026 / 1.205 x 100 = 50%