To 20 mL, 1.25 M HCl solution 30 mL of water is added to this resultant solution and again 75 mL of 0.25 M HCl in added. The molarity of the resultant solution is
A
0.40 M
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B
2.10 M
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C
0.35 M
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D
5.5 M
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Solution
The correct option is C 0.35 M In first case M1V1=M2V2 here, M1=1.25M;V1=20mL;V2=50mL So M2=1.25×2050=0.5M Now, to this 0.5 M of 50 mL HCl solution, 75 mL of 0.25 M HCl is added. Using, M3=M1V1+M2V2V3 where V3=50+75=125 mL M3=(0.5×50)+(75×0.25)125M3=0.35M