How much mg of iron are there in 100g of spinach.
if we burned 5.20g of spinach and added 10 ml of 2.0 M HCl into the spinach ashes.Then filtered the ashes and used 5 ml of that solution to put it in a testube and added 5 ml of 1.5 M KSCN in the testube. We then use a spectrometer to determine its absorbance, which is 0.353. How do I solve this
The parameter found was a=4.43236 Lmmol−1=4.43236 mM−1a=4.43236 Lmmol−1=4.43236 mM−1.
Calculate the Concentration of Fe Ions Present
You have measured an absorbance of 0.015 with a corresponding concentration of cmeas=3.38⋅10−3 mmolL−1cmeas=3.38⋅10−3 mmolL−1.
The mass of iron in the solution is given by
mFe=cmeas⋅MFe⋅V=0.00378 mg
mFe=cmeas⋅MFe⋅V=0.00378 mg
with the volume V=0.02 LV=0.02 L and molar mass MFe=55.845 gmol−1MFe=55.845 gmol−1.
To solve this problem, we need to use a series of steps based on the given information. Here's a breakdown of how to approach it:
1. First, let's calculate the moles of HCl used to react with the spinach ashes:
Moles of HCl = volume (in L) x concentration (in M)
= 10 mL x 0.001 L/mL x 2.0 M
= 0.02 moles
2. Since HCl and KSCN react in a 1:1 ratio, the moles of KSCN used will be the same as the moles of HCl used. Therefore, the moles of KSCN used is also 0.02 moles.
3. Next, we can calculate the iron(III) thiocyanate formed using the equation:
Fe3+ + 3SCN- → Fe(SCN)3
Since the ratio is 1:3, the moles of Fe(SCN)3 formed will be:
Moles of Fe(SCN)3 = moles of KSCN x 3
= 0.02 moles x 3
= 0.06 moles
4. Given that the solution has an absorbance of 0.353, we can now use the Beer-Lambert Law to calculate the concentration of Fe(SCN)3:
A = εbc
Where:
A = Absorbance
ε = Molar absorptivity or molar absorption coefficient (L·mol⁻¹·cm⁻¹)
b = Path length (cm)
c = Concentration of Fe(SCN)3 (mol/L)
In this case, we know:
A = 0.353 (given)
ε = unknown
b = unknown
c = 0.06 mol/5 mL
5. To determine the concentration of Fe(SCN)3, we divide its moles by the volume (in L):
Concentration of Fe(SCN)3 = moles of Fe(SCN)3 / volume (in L)
The volume is initially given in mL, so we need to convert it:
Volume (in L) = 5 mL x 0.001 L/mL = 0.005 L
Now we can calculate the concentration:
Concentration of Fe(SCN)3 = 0.06 moles / 0.005 L
= 12 moles/L
6. Lastly, we need to convert the concentration to milligrams. To do this, we need to know the molar mass of Fe(SCN)3, which is 188.15 g/mol.
Convert moles to milligrams:
Concentration of Fe(SCN)3 (mg/L) = 12 moles/L x 188.15 g/mol x 1000 mg/g
= 2,257,800 mg/L
Since we want to determine the amount in 100 g of spinach, we can use the equation:
Amount of Iron in 100 g of spinach = Concentration of Fe(SCN)3 (mg/L) x volume (in L) x 100 g
Plugging in the values:
Amount of Iron in 100 g of spinach = 2,257,800 mg/L x 0.005 L x 100 g
= 1,128,900 mg
Therefore, there are 1,128,900 mg of iron in 100 g of spinach.