Calculation of Molarity of H2SO4

Given:
- Concentration of H2SO4 solution: 90% (W/V)
- Density of H2SO4 solution: 1.98 g/mL

To calculate the molarity of H2SO4, we need to determine the number of moles of H2SO4 present in 1 liter of the solution.

Step 1: Calculation of the Mass of H2SO4
The concentration of H2SO4 is given as 90% (W/V), which means that 90 grams of H2SO4 is present in 100 mL of solution.

To calculate the mass of H2SO4 present in 1 liter (1000 mL) of solution, we can use the following formula:

Mass of H2SO4 = (Concentration of H2SO4 / 100) × Volume of solution

Mass of H2SO4 = (90 / 100) × 1000 mL = 900 g

Step 2: Calculation of the Number of Moles of H2SO4
The molar mass of H2SO4 is calculated by adding the atomic masses of its constituent elements:
H = 1 g/mol
S = 32 g/mol
O = 16 g/mol (there are 4 oxygen atoms in H2SO4)

Molar mass of H2SO4 = (2 × 1) + 32 + (4 × 16) = 98 g/mol

To calculate the number of moles of H2SO4, we can use the following formula:

Number of moles = Mass of H2SO4 / Molar mass of H2SO4

Number of moles = 900 g / 98 g/mol = 9.18 mol

Step 3: Calculation of Molarity
Finally, to calculate the molarity of H2SO4, we divide the number of moles of H2SO4 by the volume of the solution in liters:

Molarity = Number of moles / Volume of solution (in liters)

Since we have 1 liter of solution, the molarity can be calculated as:

Molarity = 9.18 mol / 1 L = 9.18 M

Therefore, the molarity of the 90% (W/V) H2SO4 solution is 9.18 M.