1.

On litre of 0.15 M Na_(2)SO_(3) aqueons solution is mixed with 500 mL of 0.2 M K_(2)Cr_(2)O_(7) aqueous solution in acid medium. What is the number of moles of K_(2) Cr_(2)O_(7) remaining in the solution after the reaction ?

Answer»

0.1
0.0125
0.025
0.05

Solution :When `0.15 M Na_(2)CO_(3)` (1L) mixed with `0.2 M K_(2)Cr_(2)O_(7)(5L)` than TOTAL molarity (M)
`M=(M_(1)V_(1)+M_(2) V_(2))/(V_(3))`
`M=(0.15xx1+0.2xx0.5)/(1 cdot 5)`
M=0.15 mol/L
Remaining mole of `K_(2) Cr_(2)O_(7) =0.2-0.15`
`=0.05` mol/L


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