Answer
7.5 g of mannitol were given to the patient.
Work Step by Step
$25\%$ (m/v) $ mannitol $ solution : $$ 25 \space g \space mannitol = 100 \space mL \space solution$$
$$30.0 \space mL \space solution \times \frac{25 \space g \space mannitol}{100 \space mL \space solution} = 7.5 \space g \space mannitol $$
