Answer :

To calculate the mass of 0.0091 mol of retinoic acid (C20H28O2), we need to find the molar mass of retinoic acid and then multiply it by the number of moles.The molar mass of retinoic acid (C20H28O2) can be calculated as follows:Molar mass of carbon (C) = 12.01 g/mol

Molar mass of hydrogen (H) = 1.008 g/mol

Molar mass of oxygen (O) = 16.00 g/molMolar mass of retinoic acid (C20H28O2):

= (20 × 12.01 g/mol) + (28 × 1.008 g/mol) + (2 × 16.00 g/mol)

= 240.2 g/mol + 28.224 g/mol + 32.00 g/mol

= 300.424 g/molNow, to find the mass of 0.0091 mol of retinoic acid, we use the formula:Mass = Number of moles × Molar massMass = 0.0091 mol × 300.424 g/mol

Mass ≈ 2.73 gramsTherefore, the mass of 0.0091 mol of retinoic acid is approximately 2.73 grams.