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Answer:
7.3
Explanation:
By Henderson Hasselbalch equation we can calculate the pH or the pOH of a solution by its pKa. Remember that , and pKa = -logKa. Ka is the equilibrium constant of the acid.
Henderson Hasselbalch equation :
Where [HA] is the concentration of the acid, and is the concentration of the anion which forms the acid.
So, acid X, has two ionic forms, the carboxyl group and the other one. First, we have 0.1 mol/L of the acid, in 100 mL, so the number of moles of X
n1 = (0.1 mol/L)x(0.1 L) = 0.01 mol
When it dissociates, it forms 0.005 mol of the carboxyl group and 0.005 mol of the other group. Assuming same stoichiometry.
Adding NaOH, with 0.1 mol/L and 75 mL, the number of moles of will be
n2 = (0.1 mol/L)x(0.075 L) = 0.0075 mol
So, the 0.0075 mol of reacts with 0.005 mol of carboxyl, remaining 0.0025 mol of
, which will react with the 0.005 mol of the other group. So, it will remain 0.0025 mol of the other group.
The final volume of the solution will be 175 mL, but both concentrations (the acid form and ionic form) have the same volume, so we can use the number of mol in the equation.
Note that, the number of moles of the acid form is still 0.01 mol because it doesn't react!
So,
6.72 = pKa - log 4
pKa - log4 = 6.72
pKa = 6.72 + log4
pKa = 6.72 + 0.6
pKa = 7.3
Explanation:
A balanced chemical equation is defined as the one that contains same number of atoms on both reactant and product side.
Whereas a chemical reaction that brings change in oxidation state of the reacting species is known as a redox reaction.
When there occurs decrease in oxidation number of an element then it shows the element has been reduced. And, if there occurs an increase in oxidation state of an element then it means the element has been oxidized.
(a) The reaction between nitrogen and hydrogen to form ammonia will be as follows.
So here, oxidation state of nitrogen is changing from 0 to -3. Whereas oxidation state of hydrogen is changing from 0 to +3.
Reaction between ammonia and nitric acid will be as follows.
Since, it is a combination reaction. Therefore, no change in oxidation state of reacting species is taking place.
(b) Reaction for conversion of liquid bromine to hydrogen bromide is as follows.
Here, oxidation state of hydrogen is changing from 0 to +1. Therefore, oxidation of hydrogen is taking place. On the other hand, oxidation state of bromine is changing from zero to -1. Therefore, reduction of bromine is taking place.
(c) Reaction between Zn and S will be as follows.
Here, oxidation state of zinc is changing from 0 to +2. Hence, oxidation of zinc is taking place.
Oxidation state of sulfur is changing from 0 to -2. Therefore, reduction of sulfur is taking place.