In a 25-mL volumetric flask, use pipettes to introduce 2.5 mL of 0.040-M aniline

Question

In a 25-mL volumetric flask, use pipettes to introduce 2.5 mL of 0.040-M aniline + 2.5 ML of KH2PO4 +1.5 mL of 1.00 M NaOH. Add water to a total volume of about 20 mL and equilibrate this mixture and in a separate vessel the 0.040 M I2 in 1.20 M KI. After about 10 minutes, pipette 2.5 mL of the 0.040 M 12 in 1.20 M KI solution into the reaction vessel, dilute to the 25 mL mark, and mix well. Start the clock and transfer the reaction mixture to a spectrometer cell. Read the absorbance every 5 to 10 minutes for about 1 hour.

Explanation / Answer

Molarity is the concentration of a solution expressed as the number of moles of solute per liter of solution means

Molarity (M) = (Moles of Solute/Lits solution)

for example, as given in the question 1M NaOH solution, means 1 moles of sodium hydroxide in every lit of the solution.

now if you have to prepare I2 solution:

first, you have to calculate the molecular weight of the I2 = 126

Next, you have to calculate the moles, you are preparing 0.040 M so

Mole = Weight / Molecular weight

so, weight = mole*moecular weight

= 0.040 * 126

=5.04 g

so you have to weight 5.04 g of iodine and dissolve in 1000 ml of water, then you will got the 0.040 M iodine solution

if you want to prepare in 250 ml then for that you will need (250 * 5.04)/1000 = 1.2 g

For aniline

you have to calculate in the volumetric method C1V1 =C2V2

now if you have to prepare 250 ml of 0.040 M aniline solution

then C2 = 0.040, V2= 250 ml, C1 = 10.7 (Standard solution concentration)

so V1= (0.04* 250)/ 10.7

= 0.93 ml

so you have to dissolve 0.93 ml of aniline (standard) and dissolve it to 250 ml of water to have 0.040 M aniline solution.

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