Question

how many grams of glucose is necessary to dissolve in 3 litres of water to obtan 40% solution

Answer 1

Hey there

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The correct answer is:
Let x gms of glucose dissolve in 3 liters of water to form a 40% solution.
glucose weight = x
water weight = 3 liters = 3000 g (take water density as 1.00 g/mL)
so total solution weight = x + 3000 g

glucose percent ---> x / (x + 3000) = 0.40 <--- that's the 40%

x = 0.4 ( x + 3000)
x = 0.4x + 1200
x - 0.4x = 1200
0.6 x = 1200
x = 2000 g
Are you referring to a 40% mass/volume solution? If so...
40% = 40g/100 ml
40g/100 ml x 3000 mls = 1200 grams glucose (1.2 kg)

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Hope this helps you
By jerman