Answer:
17 mg/ml.
Explanation:
Since NaOH was titrated against Citric acid in the grape fruit, therefore
Converting g to mg,
0.1698 g * 1000 mg/1 g
= 169.8 mg
Volume of grapefruit juice = 10 ml
Mass of Citric acid in ml of juice = 169.8/10
= 17 mg/ml.