Answer
(a) 7.640 %
(b) 3.498 %
(c) 4.64 %
Work Step by Step
Mass percent = (Mass solute X 100)/ (Mass solute + Mass solvent)
(a) 41.2 g $C_{12}H_{22}O_{11}$ in 498 g $H_{2}O$
= (41.2 X 100)/ (498 + 41.2)
= 4120/539.2
= 7.640 %
(b) 178 mg $C_{6}H_{11}O_{6}$ in 4.91 g $H_{2}O$
= (178 X 10^-3 X 100)/ (0.178 + 4.91)
= 17.8 / 5.088
= 3.498 %
(c) 7.55 g NaCl in 155 g $H_{2}O$
= (7.55 X 100)/(7.55+155)
= 755/162.55
= 4.64 %