Answer
0.0260 M
Work Step by Step
Molarity of $CaC_{2}O_{4}$=$ \frac{Number\,of\,moles\,of\,CaC_{2}O_{4}}{Volume\, of\, solution\,in\,L}=\frac{\frac{Mass\,in\,grams}{Molar\,mass}}{Volume\,of\, solution\,in\,L}$
$=\frac{\frac{2.50\,g}{128.1\,g/mol}}{0.750\,L}=0.0260\,M$