Question -The volume of water that must be added to a mixture of 250 ml of 0.6 M HCl and 750 ml of 0.2 M HCl to obtain 0.25 M solution of HCl is
Options:
A .  750 ml
B .  100 ml
C .  200 ml
D .  300 ml
Answer: Option C : C We can see that the number of moles of HCl should remain constant, as per the law of conservation of mass. Since we have molarity, we can calculate number of moles using, No. of moles = Molarity × volume of solution Initial Number of moles = 250 × 0.6 + 0.2 × 750 Final number of moles = 0.25 (250 + 750 + Vrequired) Equating, we get Vrequired=0.6×250+0.2×7500.25−[1000]=200ml
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