To calculate the mass of an acid required to prepare a specific volume and concentration of a solution, you need to consider the molar mass of the acid. In this case, we will calculate the mass of sulfuric acid (H2SO4) required to prepare 250 cm³ of a 0.05 M solution. Here's the step-by-step calculation:
Determine the number of moles required using the formula:
Moles = Volume (in liters) × Concentration (in moles per liter)
Convert the volume from cm³ to liters:
Volume = 250 cm³ ÷ 1000 cm³/L = 0.25 L
Moles = 0.25 L × 0.05 mol/L = 0.0125 mol
Identify the molar mass of sulfuric acid (H2SO4). You can find the atomic masses of hydrogen (H), sulfur (S), and oxygen (O) in the periodic table.
Hydrogen (H) = 1.00784 g/mol Sulfur (S) = 32.06 g/mol Oxygen (O) = 15.999 g/mol
Multiply the atomic masses by the respective subscripts in the formula and sum them up:
Molar mass of H2SO4 = (2 × Hydrogen) + Sulfur + (4 × Oxygen) = (2 × 1.00784 g/mol) + 32.06 g/mol + (4 × 15.999 g/mol) = 98.087 g/mol
Calculate the mass of sulfuric acid required using the formula:
Mass = Moles × Molar mass
Mass = 0.0125 mol × 98.087 g/mol ≈ 1.23 g (rounded to two decimal places)
Therefore, approximately 1.23 grams of sulfuric acid (H2SO4) would be required to prepare 250 cm³ of a 0.05 M solution.