One solution contains 55 g #NaCl # per liter. and another contains 55 g #KCl# per liter. Which solution has the higher molarity? How can you tell?

The number of solute particles may be determined by calculation of the molar quantities of each reagent. #NaCl# has a molar mass of #58.44# #g*mol^-1#; #KCl# has a molar mass of #74.55# #g*mol^-1#. What does this mean? It means that the given mass of stuff corresponds to a given numerical quantity of that stuff.

If equal masses of the salts are added to the same volume, clearly there will be more sodium chloride solute particles, because the molar mass of sodium chloride is smaller.

1. Since you're given the masses of each compound, all you have to do is to calculate its formula masses;
2. After that, find the no. of moles of each compound using the formula:

number of mol=mass/formula mass

1. Then find the Molarity(M) of each solution by using the formula

M=mol of solute/liters solution

1. Compare the results per your calculation to determine which solution has higher M.

Molarity is defined as the number of moles of substance dissolved per litre of solution.

The molar masses are #"58.44 g/mol"# for #"NaCl"#, and #"74.55 g/mol"# for #"KCl"#. So the numbers of moles in each case are #"0.941 moles"# of #"NaCl"# and #"0.738 moles"# of #"KCl"#.

Volumes of solution in each case are the same, 1 litre. So #"NaCl"# has the higher molarity.