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Answer:
The pH of saturated solution of the quinine is 10.05
Explanation:
Quinine (Q) is C20H24N2O2 has a molar mass of 324.4 g/mol
Q can behave as a weak base. Kb and pKb can be calculated for weak bases
pKb1 is to be considered when solving the question.
pKb1 = 5.1
Step 1 : Calculate the Kb of Quinine
pKb1 = - log [kb]
5.1 = - log [kb]
take Antilog of both side
[kb] = 7.94 x 10∧-6
Step 2: Calculate the concentration of saturated solution of Q in mol/dm3
From the question, 1900 ml of solution contains 1 g of Q
Therefore, 1000 ml of solution will contain........... x g of Q
x = 1000 /1900
x = 0.526 g in 1 dm3
In calculating concentration in mol/dm3,
Concentration in mol/dm3 = concentration in g /dm3 divided by molar mass
Molar mass of Q = 324.4
Concentration in mol/dm = 0.526 /324.4
= 0.0016 mol/dm3
Step 3: Calculating the Concentration of OH-
At Equilibrium, Kb = x² / 0.0016
7.94 x 10∧-6 = x² / 0.0016
x = √ 0.0016 × 7.94 x 10∧-6
x = 1. 127 × 10∧-4 mol/dm3
The concentration of OH- = 1. 127 × 10∧-4 mol/dm
Step 4: Calculating the pH of Quinine
Recall, pOH = - log [OH-]
pOH = - log [1. 127 × 10∧-4]
pOH = 3.948
Also recall that pH + pOH = 14
pH = 14 - 3.948
pH = 10.05
Answer: C9H11O3N
Explanation:
The percentage by mass of each element is divided by its relative atomic mass. The lowest ratio is now observed. Each ratio is now divided by this lowest ratio and approximated to whole numbers. All these are shown in detail in the image attached.
