What is the concentration of FeNCS2+ in solution 1? Solutions 2, 3, 4, 5, 6,? CI

Question

What is the concentration of FeNCS2+ in solution 1? Solutions 2, 3, 4, 5, 6,?

CIl le cuvette into the spectrophotometer; set the wavelength to 447 nm, and adjust the light control knob until the meter reads zero absorb- ance (100 %T) at 447 nm. Save this reference cuvette for periodic calibration checks. Rinse the second cuvette with solution 2, discarding the rinse into the waste beaker; then measure the absorbance and transmittance of solution 2 at 447 nm. Repeat this process with solutions 3 through 6. Prepare your calibra- tion curve by plotting absorbance versus concentration as in Figure 22.2. You should submit this curve with your report sheet. TABLE 22.1 Standard Solutions for FeNCS2* Ion Beer-Lambert Plot Solution ml of 2.00 x 10-'M Fe(NO3), in 0.10 M HNO3 mL of 2.00 x 10 M NasCN in 0.10 M HNO3 Total volume (mL) 10.00 10.00 10.00 O Un A w N 10.00 0.00 1.00 2.00 3.00 4.00 5.00 50.00 50.00 50.00 50.00 50.00 50.00 10.00 10.00 Meter - Wavelength control S Wavelength scale

Explanation / Answer

Reaction is

Fe3+ + SCN- ..............> [Fe(SCN)]2+

solution 1:

as the volume of NaSCN = 0.00 ml, so [Fe(SCN)]2+ can not formed.

[Fe(SCN)2+] = 0.00 M

Solutions 2:

1 ml of 2.00 * 10^-3 NaSCN = 0.001 * 2.00 * 10^-3 = 2.00 * 10^-6 mole.

2.00 * 10^-6 mole Fe(SCN)2+ formed.

total volume = 50 ml

so [Fe(SCN)2+] = 2.00 * 10^-6 * 1000 / 50 = 4.00 * 10^-5 M

solution 3:

2 ml of 2.00 * 10^-3 NaSCN = 0.002 * 2.00 * 10^-3 = 4.00 * 10^-6 mole.

10.0 ml of 2.0010^-1 M Fe(NO3)3 = 0.010 * 2.00 * 10^-1 = 2.00 * 10^-3 mole.

4.00 * 10^-6 mole Fe(SCN)2+ formed.

total volume = 50 ml

so [Fe(SCN)2+] = 4.00 * 10^-6 * 1000 / 50 = 8.00 * 10^-5 M

, solution 4:

3 ml of 2.00 * 10^-3 NaSCN = 0.003 * 2.00 * 10^-3 = 6.00 * 10^-6 mole.

6.00 * 10^-6 mole Fe(SCN)2+ formed.

total volume = 50 ml

so [Fe(SCN)2+] = 6.00 * 10^-6 * 1000 / 50 = 1.20 * 10^-4 M

solution 5:

4 ml of 2.00 * 10^-3 NaSCN = 0.004 * 2.00 * 10^-3 = 8.00 * 10^-6 mole.

8.00 * 10^-6 mole Fe(SCN)2+ formed.

total volume = 50 ml

so [Fe(SCN)2+] = 8.00 * 10^-6 * 1000 / 50 = 1.60 * 10^-4 M

solution 6:

5 ml of 2.00 * 10^-3 NaSCN = 0.005 * 2.00 * 10^-3 = 1.00 * 10^-5 mole.

1.00 * 10^-5 mole Fe(SCN)2+ formed.

total volume = 50 ml

so [Fe(SCN)2+] = 1.00 * 10^-5 * 1000 / 50 = 2.00 * 10^-4 M

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