Answer:
a. pka = 3,73.
b. pkb = 10,27.
Explanation:
a. Supposing the chemical formula of X-281 is HX, the dissociation in water is:
HX + H₂O ⇄ H₃O⁺ + X⁻
Where ka is defined as:
![ka = \frac{[H_3O^+][X^-]}{[HX]}](https://tex.z-dn.net/?f=ka%20%3D%20%5Cfrac%7B%5BH_3O%5E%2B%5D%5BX%5E-%5D%7D%7B%5BHX%5D%7D)
In equilibrium, molar concentrations are:
[HX] = 0,089M - x
[H₃O⁺] = x
[X⁻] = x
pH is defined as -log[H₃O⁺]], thus, [H₃O⁺] is:
![[H_3O^+]} = 10^{-2,40}](https://tex.z-dn.net/?f=%5BH_3O%5E%2B%5D%7D%20%3D%2010%5E%7B-2%2C40%7D)
[H₃O⁺] = <em>0,004M</em>
Thus:
[X⁻] = 0,004M
And:
[HX] = 0,089M - 0,004M = <em>0,085M</em>
![ka = \frac{[0,004][0,004]}{[0,085]}](https://tex.z-dn.net/?f=ka%20%3D%20%5Cfrac%7B%5B0%2C004%5D%5B0%2C004%5D%7D%7B%5B0%2C085%5D%7D)
ka = 1,88x10⁻⁴
And <em>pka = 3,73</em>
b. As pka + pkb = 14,00
pkb = 14,00 - 3,73
<em>pkb = 10,27</em>
I hope it helps!
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The final temperature of the lead-water system will be lower than the final temperature of the copper-water system.
Hello!
To do this, use the molar mass. This is how much a mole of an atom weighs. A mole is 6.02214076×10²³ atoms.
Molar masses of:
Se: 78.96 g/mol
Cu: 63.546 g/mol
Ba: 137.327 g/mol
Now, the element with the highest molar mass will have the fewest atoms. This is because the element weighs more, so therefore for the same amount of mass, there will be less of the element needed to reach that mass.
Therefore, 10g of Ba would have the fewest number of atoms.
Hope this helps!
The given concentration of boric acid = 0.0500 M
Required volume of the solution = 2 L
Molarity is the moles of solute present per liter solution. So 0.0500 M boric acid has 0.0500 mol boric acid present in 1 L solution.
Calculating the moles of 0.0500 M boric acid present in 2 L solution:
Converting moles of boric acid to mass:
Therefore, 6.183 g boric acid when dissolved and made up to 2 L with distilled water gives 0.0500 M solution.
