Part B Data Table step 1) volume volume molarity molarity test | 0.0024M | 0.004

Question

Part B Data Table step 1) volume volume molarity molarity test | 0.0024M | 0.0040M | [CrOu.q2 [Ag,Al Ago)quotient precipitate mL mL yes/no What can be stated with certainty about the numerical value of Ksp AsCo, at this point? step 2) molar absorption coefficient L/mol volume volume molarity absorbance test | 0.0024M| 55.6M | [CrOuaq at 380nm tube K2C) H20 mL. mL mol/L 2.50 0. 58 0.28 0. 0 8 0.03 average molar absorption coefficient molar absorption coefficient = absorbance ÷ molarity calculations

Explanation / Answer

In the step 1, we are given with two different sets of readings.

In reading 1, we are provided with 3 ml of aq. Solution of K2CrO4 and 3 ml of AgNO3.

So, after mixing the two solutions, the total volume will be 6 ml .

So, Molarity of CrO4- in the mixture will be 0.0024*3/6

Which is equal to 0.0012 M

Similarly the concentration of Silver ions in the mixture will be 0.0020 M. We must not forget that during the mixing 2 moles of KNO3 salt will get precipitated out.

Also, In the formation of Ag2CrO4  2 moles of silver ions and one mole of chromate ions are used.

Now, Ksp for this formation will be

[CrO42-]* [Ag+]2 = 0.0012*0.0020 = 0.24*10-5.

Similarly, for the second set of readings Ksp will be 0.0024*2/6 *( 0.004*4/6) = 0.2133* 10-5.

Now for the second part of the above question,

The approach is

Absorbance = molar absorbance coefficient * concentration * length of cuvettee.

Length according to standard notation is 10 dm but we will take it 1 cm for this case.

Now we need to find the slope of Abs. V/S concentration plot.

From mathematics of linear equation we know that,

Slope = (Y2 -Y1)/(X2-X1)

So, molar absorption coeff. will be (2.5-0.28)/((3-1)/5)*0.0024 = 2.22*5/(2*0.0024) =2312.5 M-1Cm-1

We must note that we have considered the total volume of each testubes to be 5ml and 1 ml change for all five testubes.

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