200 mL of 0.5 M, 300 mL of 0.7 M and 500 ml of 2 M solutions of ethanol are mixed. The final solution is diluted by 10 times. Its molarity is:
A
1.31 M
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B
13.1 M
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C
0.131 M
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D
131 M
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Solution
The correct option is C 0.131 M No.ofmoles=molarity×volume(inlitre
Hence, No.ofmolesin200mL0.5M=0.5×2001000=0.1 No.ofmolesin300mL0.7M=0.7×3001000=0.21No.ofmolesin500mL2.0M=2.0×5001000=1.0
Now, Totalno.ofmoles=0.1+0.21+1=1.31 TotalVolume=(200+300+500)mL=1000mL=1L Molarityofsolutionaftermixing=1.311=1.31M
After 10 times dilution,
Molarity = 0.131 M