Question

$5.85g$ of $NaCl$ is dissolved in $1L$ of pure water. The number of ions in $1mL$ of this solution is

• A. $6.02\times 10^{19}$
• B. $1.2\times 10^{22}$
• C. $1.2\times 10^{20}$
• D. $6.02\times 10^{20}$

Answer 1

Answer: (C)

Number of molecules of $NaCl$ in $1L$ water

$=\frac{5.85}{58.5}\times 6.023\times 10^{23}=6.023\times 10^{22}$ molecules

Number of molecules of $NaCl$ in one $mL$ solution

$=\frac{6.023\times 10^{22}}{1000}=6.023\times 10^{19}$

$NaCl\to N{a}^{+}+C{l}^{-}$

One molecule gives $2$ ions.

$\therefore$ Number of ions in one $mL$ solution

$=6.023\times 10^{19}\times 2=1.2\times 10^{20}$