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peterradu47781
06.10.2019 •
Chemistry
Just as ph is the negative logarithm of [h3o+], pka is the negative logarithm of ka, pka=−logka the henderson-hasselbalch equation is used to calculate the ph of buffer solutions: ph=pka+log[base][acid] notice that the ph of a buffer has a value close to the pka of the acid, differing only by the logarithm of the concentration ratio [base]/[acid]. the henderson-hasselbalch equation in terms of poh and pkb is similar. poh=pkb+log[acid][base] part apart complete acetic acid has a ka of 1.8×10−5. three acetic acid/acetate buffer solutions, a, b, and c, were made using varying concentrations: [acetic acid] ten times greater than [acetate], [acetate] ten times greater than [acetic acid], and [acetate]=[acetic acid]. match each buffer to the expected ph. drag the appropriate items to their respective bins. view available hint(s) ph = 3.74 [acetic acid] ten times greater than [acetate] ph = 4.74 [acetate] = [acetic acid] ph = 5.74 [acetate] ten times greater than [acetic acid] previous answers correct part b how many grams of dry nh4cl need to be added to 2.20 l of a 0.400 m solution of ammonia, nh3, to prepare a buffer solution that has a ph of 8.89? kb for ammonia is 1.8×10−5
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Ответ:
You need to add 109,2g of NH₄Cl.
Explanation:
To calculate the pH in a buffer you can use Henderson-Hasselbalch formula:
pH = pka + log₁₀![\frac{[base]}{[acid]}](/tpl/images/0291/7684/a552b.png)
1. ka of 1,8x10⁻⁵ ≡ 4,74
pH = 4,74 + log₁₀
= 3,74
pH = 4,74 + log₁₀
= 4,74
pH = 4,74 + log₁₀
= 5,74
2. Using:
pOH = pkb + log₁₀![\frac{[acid]}{[base]}](/tpl/images/0291/7684/81b45.png)
A pH of 8,89 is a pOH of 14-8,89 = 5,11
Thus:
5,11 = 4,74 + log₁₀![\frac{[acid]}{[base]}](/tpl/images/0291/7684/81b45.png)
2,32 =![\frac{[acid]}{[base]}](/tpl/images/0291/7684/81b45.png)
The moles of ammonia (base) are:
2,20L × 0,400M = 0,88 moles
Replacing:
2,32 =![\frac{[acid]}{[0,88]}](/tpl/images/0291/7684/6493b.png)
[acid] = 2,0416 moles of NH₄Cl ₓ (53,491g/mol) = 109,2 g of NH₄Cl
You need to add 109,2g of NH₄Cl.
I hope it helps!
Ответ:
answer 24°
Step-by-step explanation:
two sides are equal so it is isosceles triangle
<BCE+90°+66°= 180
<BCE=24°
now,
<FCA=<BCE (vertical opposite angle)
<FCA=24°