Question 62

Suppose that a maximum of 25 g of salt dissolves in 100 g of water. Any more salt, if added, remains undissolved and a sediment falls at the bottom. Now, water is evaporated from 1 kg of a 4% solution at the rate of 28 g per hour. After how long will it start sedimenting, approximately?

Solution

25 gm salt in 100 gm water

1 gm = 100/25

40 gm = 100/25 * 40 = 160 gm

Water is evaporated at 28 gms per hour

From option C, we get

after 30 hrs

water loss = 30*28

= 840

Present value of water = 1000 - 840 = 160 gms

After 30 hrs, water will start to reduce and salt will begin to sediment.

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