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Preparing standards for a calibration curve.

(a) How much ferrous ethylene diammonium sulfate(FeH3NCH2CH2NH3SO42⋅4H2O,FM382.15)should be dissolved in a 500mL volumetric flask with1MH2SO4to obtain a stock solution with~500μgFe/mL2?

(b) When making stock solution (a), you actually weighed out 1.627 g of reagent. What is the Fe concentration in role="math" localid="1668357579931" 500μgFe/mL2?

(c) How would you prepare 500 mL of standard containing 1,2,3,4, and5μgFe/mL2in0.1MH2SO4infrom stock solution (b) using any Class A pipets from Table 2-4 with only 500 -mL volumetric flasks?

(d) To reduce the generation of chemical waste, describe how you could prepare 50 mL of standard containing, andinfrom stock solution (b) by serial dilution using any Class A pipets from Table 2-3 with only 50mL volumetric flasks?

Short Answer

Expert verified

a) m = 1.712g

b) γ= 475.8 μ²µ/mL

c)4.75μ²µ/mL

Step by step solution

01

Find mass of ferrous ethylenediammonium sulfate

First we calculate mass of Fe in 500mL:

m=500⋅10−6g/mL⋅500mLm=0.25g

The n is:

n(Fe)=0.25g55.85g/moln(Fe)=4.48⋅10−3mol

m=4.26⋅10−3g⋅55.85g/molm=0.2379g

The mass of ferrous ethylenediammonium sulfate is:
02

Find y (concendration)

b) First, we calculate n of reagent

n=1.627g382.15g/moln=4.26⋅10−3mol

The mass of Fe is:

m=4.26⋅10−3g⋅55.85g/molm=0.2379g

In one mL is:

0.2379g500mL=4.758⋅10−4g/mL

In μ²µ/mLis:

γ=475.8μ²µ/mL

03

Find concentration for  different dilution

c) To prepare 500mL of1μ²µ/mL,we need to dilute 1mL of stock solution to 500mL with 0.1MH2SO4 to obtain:

1mL500mL×475.8μg/mL=0.9516μg/mL

To prepare 500mL of2μ²µ/mL , we need to dilute 2mL of stock solution to 500mL with0.1MH2SO4 to obtain:

2mL500mL×475.8μg/mL=1.9032μg/mL

To prepare 500 of 3μ²µ/mL, we need to dilute 3mL of stock solution to 500mL with0.1MH2SO4 to obtain:

3mL500mL×475.8μg/mL=2.855μg/mL

To prepare 500 of 4μ²µ/mL, we need to dilute 4mL of stock solution to 500mL with0.1MH2SO4 to obtain:

To prepare 500 of5μ²µ/mL ,we need to dilute 5mL of stock solution to 500mL with0.1MH2SO4 to obtain:

5mL500mL×475.8μg/mL=4.758μg/mL

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In formaldehyde, the transition n→π*(T1)occurs at 397 nm,and the n→π*(S1)transition comes at 355 nm. What is the difference in energy (kJ/mol) between the S1andT1states? This difference is due to the different electron spins in the two states.

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Total role="math" localid="1663647483742" μ³¢Pb2+added

Absorbance at 490nmwavelength

Total μ³¢Pb2+added

Absorbance at490nmwavelength

0.0

6.0

12.0

18.0

24.0

30.0

36.0

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0.316

0.345

0.370

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70.0

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0.448

0.449

0.450

0.447


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