Use the periodic table to answer this question. A student dissolves 24.2 g of NaCl in 500 mL of water. Another student dissolved 24.2 g of KI in 500 mL of water. Why do the two solutions have different molarities?


The volumes of the solutes differ.

The final volumes of solution are different.

The compounds have different molar masses.

The final solutions have different masses.

The final volumes of solution are different.

the molar mass of NaCl is ... 58.44 g

the molar mass of KI is ... 166.00 g

To determine why the two solutions have different molarities, we need to understand what molarity is and how it is calculated.

Molarity is a measure of the concentration of a solution. It is defined as the number of moles of solute per liter of solution. The formula for calculating molarity (M) is:

Molarity = moles of solute / volume of solution (in liters)

In this case, the volume of the solutions (500 mL) is the same, but the solutes are different (NaCl and KI). To calculate the molarity, we need to consider the number of moles of each solute.

First, we need to determine the number of moles of each solute by using the molar mass of the compounds. The molar mass is the mass of one mole of a substance and can be found on the periodic table.

The molar mass of NaCl is 58.44 g/mol. To calculate the number of moles of NaCl, we divide the mass of NaCl (24.2 g) by its molar mass:

moles of NaCl = mass of NaCl / molar mass of NaCl = 24.2 g / 58.44 g/mol = 0.414 mol

Similarly, the molar mass of KI is 166 g/mol. To calculate the number of moles of KI, we divide the mass of KI (24.2 g) by its molar mass:

moles of KI = mass of KI / molar mass of KI = 24.2 g / 166 g/mol = 0.146 mol

Now, we can calculate the molarities of the two solutions by dividing the moles of solute by the volume of the solution in liters.

For the NaCl solution:
Molarity of NaCl = moles of NaCl / volume of solution (in liters) = 0.414 mol / 0.5 L = 0.828 M

For the KI solution:
Molarity of KI = moles of KI / volume of solution (in liters) = 0.146 mol / 0.5 L = 0.292 M

Therefore, the two solutions have different molarities because the compounds have different molar masses and hence different numbers of moles per gram.