1. An aqueous solution contains 0.154 M ascorbic acid (H2C6H6O6) and 0.196 M hydrobromic acid. Calculate the ascorbate (C6H6O62-) ion concentration in this solution.
Can you explain how to do this please? thank you.
Also if you can is number 2 missing information or am I supposed to find the ka values?
2. Calculate the concentration of HCO3- in an aqueous solution of 0.0701 M carbonic acid, H2CO3 (aq)?
You can use a short cut on #1 even though the ionization I write below is not quite right. But the equation doesn't know that. :-)
H2A is ascorbic acid
H2A ==> 2H^+ + A^2-
k1k2 = (H^+)^2(A^2-)/(H2A)
Look up k1 and k2, substitute the other numbers and solve for A^2-
#2.
............H2CO3 ==> H^+ + HCO3^-
initial.....0.0701....0.......0
change.......-x.......x.......x.
equil....0.0701-x......x......x
k1 = (H^+)(HCO3^-)/(H2CO3)
Substitute the numbers into k1 and solve for x = HCO3^-. You may need to user the quadratic; i.e., x MAY not be neglected with 0.0701-x. Work it out to see.
To find the concentration of the ascorbate ion (C6H6O62-) in the solution, we need to first consider the reaction between ascorbic acid (H2C6H6O6) and hydrobromic acid (HBr).
The balanced chemical equation for the reaction can be written as follows:
H2C6H6O6 + 2HBr → C6H6O62- + 2H2O + 2Br-
From the equation, we can see that one molecule of ascorbic acid reacts to produce one molecule of ascorbate ion. Therefore, for every mole of ascorbic acid reacted, one mole of ascorbate ion is formed.
Given that the concentration of ascorbic acid (H2C6H6O6) is 0.154 M, we can assume that the concentration of ascorbate ion (C6H6O62-) will also be 0.154 M.
Therefore, the concentration of the ascorbate ion in the solution is 0.154 M.
Now, moving on to the second question:
To find the concentration of HCO3- in the solution of carbonic acid, we need to consider the dissociation of carbonic acid (H2CO3).
The dissociation of carbonic acid can be represented using the following equilibrium equation:
H2CO3 ⇌ HCO3- + H+
The equilibrium constant expression for this reaction is:
Ka = [HCO3-][H+]/[H2CO3]
Given that the concentration of carbonic acid, H2CO3, is 0.0701 M, we can assume that the concentration of HCO3- will be equal to the concentration of H2CO3 that dissociates.
Assuming complete dissociation, the concentration of HCO3- will be equal to 0.0701 M.
So, the concentration of HCO3- in the solution is 0.0701 M.
Note: If the question provides the Ka value for the dissociation of carbonic acid, you may need to use it in combination with the concentration of H2CO3 to calculate the concentration of HCO3-.
To calculate the ascorbate (C6H6O62-) ion concentration in the solution, we need to consider the dissociation of ascorbic acid (H2C6H6O6). The dissociation of ascorbic acid can be represented as:
H2C6H6O6 ⇌ H+ + HC6H6O6-
From the given concentration of ascorbic acid (H2C6H6O6) as 0.154 M, it indicates that the concentration of H+ ions is also 0.154 M since the acid is monoprotic.
Since there is no information on the dissociation of hydrobromic acid (HBr), we can assume it is fully ionized in water. Therefore, the H+ concentration is given by the hydrobromic acid concentration, which is 0.196 M.
Now, we need to find the concentration of ascorbate (C6H6O62-) ions. Since ascorbic acid is a weak acid, the amount of ascorbate ions formed from the dissociation of ascorbic acid is negligible compared to its initial concentration.
Hence, the concentration of ascorbate ions (C6H6O62-) is approximately zero in this solution.
Moving on to the second question:
To calculate the concentration of HCO3- in the carbonic acid (H2CO3) solution, we need to consider the dissociation of carbonic acid. The dissociation can be represented as:
H2CO3 ⇌ H+ + HCO3-
The concentration of H2CO3 is given as 0.0701 M. Since carbonic acid is a weak acid, we can assume that only a small fraction of it dissociates, allowing us to simplify our calculations.
Let's assume x M represents the concentration of H+ and HCO3- ions formed from the dissociation. Since it is a 1:1 molar ratio, the concentration of H+ and HCO3- is also x M.
The dissociation constant (Ka) expression for carbonic acid can be written as:
Ka = [H+][HCO3-] / [H2CO3]
Given that Ka for carbonic acid is 4.2 x 10^-7, we can substitute the known values into the equation:
4.2 x 10^-7 = x^2 / 0.0701
Solving the equation for x, we find:
x = √(4.2 x 10^-7 * 0.0701)
x = 1.45 x 10^-4 M
Therefore, the concentration of HCO3- ions in the carbonic acid solution is approximately 1.45 x 10^-4 M.