In-Lab Question 2a. Would you predict the absorbance of Solution 2 to be greater

Question

In-Lab Question 2a. Would you predict the absorbance of Solution 2 to be greater than or less than that of Solution 1?

greater than

less than  

  the same

cannot tell

In-Lab Question 2b. Why?

The [Cu2+] is higher in solution 2, so less light is absorbed.

The [Cu2+] is higher in solution 2, so more light is absorbed.    

The [Cu2+] is lower in solution 2, so more light is absorbed.

The [Cu2+] is lower in solution 2, so less light is absorbed.

cannot tell from the information given

In-Lab Question 3. What is the concentration of Cu2+ in your unknown solution? Record this concentration below. (Hint: Use the absorbance of the unknown and the trendline to solve for the Cu2+concentration.)

Data Table A. Calibration Curve of Cu2+ Solutions and Unknown Stock Cu2+ solution concentration         0.498  M Wavelength 635 nm Solution # Target Volume of Cu2+, mL Actual Volume of Cu2+, mL Target Volume of H2O, mL Actual Volume of H2O, mL [Cu2+], M (calculated) Absorbance at ~660 nm (measured to the 0.0001 decimal place) 1 1.50 1.50 6.50 6.50 .0934 .2347 2 3.00 3.00 5.00 5.00 .187 .4759 3 4.50 4.50 3.50 3.50 .280 .7445 4 6.00 6.00 2.00 2.00 .374 .9021 Equation of Trendline:   y = 2.476  x + .01   R2 = .9972  Check the number of significant figures.

Explanation / Answer

1. The absorbance of Solution 2 would be greater than the absorbance of Soluion 1.

2. The [Cu2+] is higher in solution 2, so more light is absorbed.

3. the absorbance for the unknown is not given.

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