Question

What is the molaritiy of a 50.0mL aqueous solution contains 10.0 grams of table salt,NaCl

Answer 1

The molarity is 3.42
`(moles)/(liter)`

Step-by-step explanation:

The molarity reflects the concentration of a solution and indicates the number of moles of solute per liter of solution. In other words, the molarity (M) is the number of moles of solute that are dissolved in a given volume.

The Molarity of a solution is determined by the following formula:

`Molarity (M)=(number of moles of solute)/(volume)`

Molarity is expressed in units (
`(moles)/(liter)`).

To know the amount of moles of solute (NaCl) you must know its molar mass. If:

• Na: 23 g/mole
• Cl: 35.45 g/mole

the molar mass of NaCl is: 23 g/mole + 35.45 g/mole= 58.45 g/mole

Now you apply a rule of three as follows: if 58.45 g of NaCl are present in 1 mole, 10 grams of the compound in how many moles are they?

`moles=(10 g*1 mole)/(58.45 g)`

moles= 0.171

Then:

• number of moles of solute: 0.171 moles
• volume= 50 mL= 0.05 L (being 1 L=1000 mL)

Replacing in the definition of molarity:

`Molarity=(0.171 moles)/(0.05 L)`

Molarity= 3.42
`(moles)/(liter)`

The molarity is 3.42
`(moles)/(liter)`