100 g of H2O and glucose contains 9 g of glucose and 91 g H2O. The MW of glucose is 180.156 g/mol. Therefore, this 100 g contains 0.05 moles of glucose. The H2O is 18 g/mol and therefore this sample has 5.06 moles of H2O. Molar concentration is defined as moles of substance A divided by the total moles of A and all other substances in the solution. Therefore, glucose Mc=(0.05/(0.05+5.06))=0.98%. Note that the ratio of mol wt. between glucose and H2O is roughly 10, so this magnitude of change going from wt.% to mol% is consistent.