Molarity (M) = moles of the solute (mol) / Volume of the solution (L)
The molarity of the given KCl solution = 2.10 M
Volume of the given KCl solution = 85.0 mL
Hence,
2.10 M = Moles of KCl / 85.0 x 10⁻³ L
Moles of KCl = 2.10 M x 85.0 x 10⁻³ L
= 0.1785 mol
Moles (mol) = Mass (g) / Molar mass (g mol⁻¹)
Molar mass of KCl = 74.56 g mol⁻¹
Hence,
0.1785 mol = Mass of KCl / 74.56 g mol⁻¹
Mass of KCl = 0.1785 mol x 74.56 g mol⁻¹
= 13.30 g
Hence, mass of given KCl in 85.0 mL is 13.30 g.
