what is the molarity of a solution that contains 2.38g of H2C2O4·2H2O in exactly 300mL of solution?

Molar mass of H₂C₂O₄•2H₂O = (1.0×6 + 12.0×2 + 16.0×6) g/mol = 126.0 g/mol
No. of moles of H₂C₂O₄•2H₂O = (2.38 g) / (126.0 g/mol) = 2.38/126.0 mol

Volume of the solution = 300 mL = 0.3 L
Molarity of the solution = (2.38/126.0 mol) / (0.3 L) = 0.0630 M

convert the 2.38 to moles, then divide by 0.300 L

Divide by the molar mass and then by the volume