Question

A 3.0% by mass aqueous solution of hydrogen peroxide (H2O2) can be purchased at a pharmacy; by contrast, chemistry departments can purchase 30.0% by mass aqueous solution of hydrogen peroxide having a density of 1.10 g/mL at 25°C.

How many moles of hydrogen peroxide are supplied by 2.00 g of the 30.0% solution at 25°C?

How many moles of hydrogen peroxide are supplied by 2.00 mL of the 30.0% solution at 25°C.

What mass in grams of water is present in 2.00 mL of the 30.0% solution at 25°C?

How many hydrogen peroxide molecules are present per milliliter of the 30.0% solution at 25°C?

Answer 1

How many moles of hydrogen peroxide are supplied by 2.00 mL of the 30.0% solution at 25°C.

solution :

mass of solution = v*d

                 = 2*1.1 = 2.2 g

so that ,

mass of H2O2 in 2.2 g solution = 2.2*30/100 = 0.66 g

no of mol of H2O2 = w/w = 0.66/34 = 0.0194 mole

What mass in grams of water is present in 2.00 mL of the 30.0% solution at 25°C?

solution :

mass of solution = v*d

                 = 2*1.1 = 2.2 g

so that ,

mass of H2O2 in 2.2 g solution = 2.2*30/100 = 0.66 g

mass of water in solution = 2.2-0.66 = 1.54 g

How many hydrogen peroxide molecules are present per milliliter of the 30.0% solution at 25°C?

solution :

mass of solution = v*d

                 = 1*1.1 = 1.1 g

so that ,

mass of H2O2 in 1.1 g solution = 1.1*30/100 = 0.33 g

no of mol of H2O2 = 0.33/34 = 0.0097 mole

no of molecules of H2O2 = 0.0097*6.023*10^23

               = 5.84*10^21 molecule