Question

6.52 grams of sodium hydrogen carbonate is weighed into a 150 ml beaker and dissolved in 100 ml of deionized water. The solution is then quantitatively transfer to a 250.0 mL volumetric flask and filled to the line with deionized water.

What is the molarity of hydrogen carbonate in the volumetric flask?

Answer 1

Solution -

Mass of sodium hydrogen carbonate = 6.52 g

Molar mass of sodium hydrogen carbonate= 84.007 g/mol

As per information , 6.52 g of sodium hydrogen carbonate dissolve and prepared solution in 250 mL volumetric flask. So # total amount of solution = 250 .0mL , amount of solution in liter = (250.0 /1000)

= 0.25 liter

We know ,

Molarity = number of moles per liter of solution ,is called as Molarity

We have to calculate number of moles of sodium hydrogen carbonate (n) = mass (m) /molar mass (M)

= (6.52 g /84.007 g/mol)

= 0.07761 mol

Now as per definition ,

Molarity (M) = number of moles (n) / volume of solution in liter

= (0.07761 mol/0.250 liter)

=0.31 M