Given: Initial ratio = 2: 3 Final quantity = 10% acid + 90% water Capacity of glass = 100 ml Process repeated = 2 Formula used: Final Q = Initial Q × (1−(
volumeremoved
InitialQ
)n Here, n = Number of times volume taken out Calculation: Initial quantity of acid = (
2
5
) × 100 ⇒ Initial quantity of acid = 40 ⇒ Final quantity = 0.10 × 100 ⇒ Final quantity = 10 ml Now, 10 = 40 × (1 – (
X
40
)2 ⇒ 10 = 40 × (
(40–X)
40
)2 ⇒ 400 = (40–X)2 ⇒ 20 = 40 – X ⇒ X = 20 ∴ 20 ml of mixture was replaced twice with acid