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

$\begin{array}{1 1}(a)\;6.02\times 10^{20}& (b)\; 6.02\times 10^{19}\\(c)\;1.2\times 10^{20}& (d)\;1.2\times 10^{22}\end{array} $

1 Answer

Molarity of NaCl=$\large\frac{5.85}{58.5}$$\times 10^{-1}$
$\therefore$ 1ml of NaCl=$10^{-4}$mol
1 mol of NaCl=$6.023\times 10^{23}$ molecules of NaCl .But NaCl molecules are dissociated into two ions $(Na^+$ and $Cl^{-})$
$\therefore$ 1mol of NaCl =$6.023\times 10^{23}\times 2$ions.
$\therefore 1\times 10^{-4}$mole of NaCl =$6.023\times 10^{23}\times 2$ions.
$\Rightarrow 1.2\times 10^{20}$ions
Hence (c) $1.2\times 10^{20}$ions is the correct answer.
answered Mar 25, 2014 by sreemathi.v

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