Mole fraction of dextrose = moles of dextrose / total moles of solution
Total moles of solution = moles of dextrose + moles of water
Given, moles of dextrose = 0.25 mol
Moles of water = 89.48 mol
Total moles of solution = 0.25 mol + 89.48 mol = 89.73 mol
Mole fraction of dextrose = 0.25 mol / 89.73 mol = 0.0028
Rounding to 2 significant figures, the mole fraction of dextrose in the solution is 0.0028.