What is the molarity of a salt solution made by dissolving 240mg of NaCl in 4ml of water? Assume final volume is the same as the volume of water.
#"1 L" = 10^3# #"mL"#
of solution. Notice that you already know the number of milligrams of sodium chloride, the solute, present in
#10^3 color(red)(cancel(color(black)("mL solution"))) * "240 mg NaCl"/(4color(red)(cancel(color(black)("mL solution")))) = 60 * 10^3# #"mg"#
#color(blue)("1 g" = 10^3color(white)(.)"mg"#
you can say that
#60 * color(blue)(10^3color(white)(.)"mg") = 60color(white)(.)color(blue)("g")#
of sodium chloride. Now, to convert this to moles, use the molar mass of the compound
#60 color(red)(cancel(color(black)("g"))) * "1 mole NaCl"/(58.44color(red)(cancel(color(black)("g")))) = "1.027 moles NaCl"#
Since this represents the number of moles of sodium chloride present in
#color(darkgreen)(ul(color(black)("molarity = 1 mol L"^(-1)))#
The answer must be rounded to one significant figure, the number of sig figs you have for the volume of the solution.
The molarity of a solution is the concentration of moles of solute per liter of solution,
Determine moles of
Divide the mass of
Divide mol NaCl by volume of solution.