Question

a common concentration unit used commercially is percent weight per volume (%w/v) which is the number of gram of solute in 100 ml of solution. a bottle of hydrogen peroxide contains 2.5 %w/v hydrogen peroxide (h2o2). what is the molar concentration of hydrogen peroxide in the solution?

Answer 1

Answer:

• The molar concentraion is 0.74 M

Explanation:

1) Data:

a) % w/v = 2.5%

b) compound: H₂O₂ (from a table molar mass = 34.0147 g/mol)

c) M = ?

2) Formulae:

a) % w/v = (mass of soulte / volume of solution) × 100

b) numer of moles, n = mass in grams / molar mass

c) M = number of moles of solute / liters of solution

3) Solution:

a) Take a base of 100 ml of solution (0.100 liter):

• %w/v = 2.5% = 2.5 g solute / 100 ml solution

• mass of solute = 2.5 g / 100 ml × 100 ml  = 2.5 g

b) Calculate the number of moles of solute, n:

• n = mass in grams / molar mass = 2.5 g / 34.0147 g/mol = 0.0735 mol

c) Calculate the molarity, M:

• M = n / V in liter = 0.0735 mol / 0.100 liter = 0.735 M

Round to two significant figures: 0.74 M ← answer