Question

Find the molarity of a 450 mL solution containing 13.7 g of ZnSO4.​

Answer 1

The molarity is 0.189
`(moles)/(liter)`

Step-by-step explanation:

Molarity is a measure of concentration of a solution that indicates the number of moles of solute that are dissolved in a given volume. In other words, the molarity indicates the amount of moles of solute that appear dissolved in each liter of the mixture.

Molarity is determined by the expression:

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

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

So, you need to know the amount of moles of ZnSO₄. Then you must know the molar mass. If:

• Zn: 65 g/mol
• S: 32 g/mol
• O: 16 g/mol

the molar mass of ZnSO₄ is:

ZnSO₄= 65 g/mol + 32 g/mol + 4* 16 g/mol= 161 g/mol

Then you can apply a rule of three as follows: if 161 g of ZnSO₄ is contained in 1 mole, 13.7 g in how many moles are they?

`moles=(13.7 g*1 mole)/(161 g)`

moles=0.085

Then you know:

• number of moles of solute= 0.085 moles
• Volume= 450 mL (Being 1 L=1,000 mL)

Replacing in the definition of molarity:

`Molarity= (0.085 moles)/(0.45 L)`

Molarity=0.189
`(moles)/(liter)`

The molarity is 0.189
`(moles)/(liter)`