Question

If 5.85 g of NaCl are dissolved in 90 g of water, the mole fraction of NaCl is

• A. 0.1
• B. 0.01
• C. 0.2
• D. 0.0196

Answer 1

Answer: (D)

0.0196

Answer 2

Given:- Mass of $NaCl =5.85 g$ Mass of $H _{2} O =90 g$ Number of moles of $NaCl =\frac{5.85}{58.5}=0.1$ Number of moles of $H _{2} O =\frac{90}{18}=5$ Mole fraction of solute $=\frac{ n _{\text {solute }}}{ n _{\text {solute }}+ n _{\text {solvent }}}$ Mole fraction $=\frac{0.1}{5+0.1}$ $\Rightarrow X _{ B }=0.0196$