1) Diluting Concentrated Nitric Acid Calculate the volume of 15 M Nitric acid re

Question

1) Diluting Concentrated Nitric Acid
Calculate the volume of 15 M Nitric acid required to make 250 mL of 1.2 M nitric acid.
a) Volume of 15 M Nitric acid required ____20__________ mL
2) Making the Original Phosphate Solution
You weigh out pure NaH2PO4.
Weight of Sodium Dihydrogen phosphate used 0.5629 g
This is dissolved, quantitatively transfered, and diluted to 100 mL in a volumetric flask.
10 mL of this is pipetted and again diluted to 100.00 mL to make the original phosphate standard.
Calculate:
b) The phosphate concentration of this solution ______4.7________ mM

3) Making a Standard for Measurement in the Spectrometer
Volume of original phosphate standard (problem 2) used 2.15 mL
The phosphate standard, 5 mL of molybdate solution and 10 mL of dilute Nitric acid were added to a 100 mL volumetric flask, diluted to volume and mixed thoroughly.

Calculate:
c) Phosphate concentration in this standard _______________ mM

4) Measuring the Absorbance of the Standard
The solution in 3) was put in a cuvet and the %T measured at 380 nm.
% T of solution 55.8 %
% T of blank 95.3 %
Calculate:

d) Absorbance of standard _______________

5) Analysis of an Unknown
This is a separate problem and does not depend on 1, 2, 3, or 4.
3.44 mL of "Unknown Solution" were pipetted into a 100 mL volumetric flask along with the molybdate and nitric acid solutions. This was diluted to volume, mixed and measured in the spectrometer.
The absorbance of this solution was 0.425
The concentration of this solution (from standard plot) was 0.0180 mM
Calculate:
e) Concentration of the unknown solution _______________ mM
f) Concentration of the unknown solution _______________ ppm P
g) Grams of "H3PO4" in 239 mL of unknown _______________ g

Explanation / Answer

1) use dilution principal

M1V1 = M2V2

15*V1=1.2*250 = V1 20 mL

2) b 4.7 mM

plz ask the remaining problems others i am not vermuch confedent on others

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