Given a 100 mL solution (soln A) of a unknown conventraion of Cu(NH_3)_4^2+. 10m

Question

Given a 100 mL solution (soln A) of a unknown conventraion of Cu(NH_3)_4^2+. 10ml of the known solution was withdrawn and diluted to the mark in a 25 mL (soln B). soln B has absorbance value of 0.85

Calibration curve: y=53.15 - 0.004 R-squared value: 0.997

A) Calculate the molarity of the Cu(NH_3)_4^2+ solution (soln B) from which the absorbance was measured

B) Calculate the molarity of the Cu^2+ ion in the original solution corrected for dilution (soln A)

C) Calculate the number of moles of Cu^2+

Explanation / Answer

A,

A=slopexC

C=0.85/53.15=1.6x10^-2M

B.No of moles =molarityxvolume=1.6x10^-2Mx0.025L=4x10^-4

4x10^-4moles present in 10ml of the solution, then in 100ml

No of moles in sol A=4x10^-4x100/10=4x10^-3

molarity (soln A)=4x10^-3/0.1L=4x10^-2

C.No of moles in sol A=4x10^-4x100/10=4x10^-3

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