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Sveta_85 [38]
3 years ago
11

Codeine C18H21NO3 is a weak organic base. A 5.0 x 10^-3 M solution of codeine has a pH of 9.95. Calculate the value of Kb for th

is substance. What is the pKb for this base?
Chemistry
1 answer:
arsen [322]3 years ago
7 0

Answer:

Kb = 4.45\times10^{-7}\ mol/L

p^{Kb}=6.35

Explanation:

For a weak organic base, the formula to find p^{OH} is given by:

p^{OH}=p^{K_b}+\log c

where c is the concentration of base.

Here c= 5\times10^{-3}\ M

p^{H}=9.95\\p^{OH}=14-p^{H}=14-9.95=4.05

Substituting the above values in the formula,we get:

p^{k_b}=p^{OH}-\log c\\p^{k_b}=4.05-\log (5\times10^{-3})\\p^{K_b}=6.35\\K_b=$antilog 6.35=4.45\times10^{-7}\ mol/L

Hence:

Kb = 4.45\times10^{-7}\ mol/L

p^{Kb}=6.35

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Answer:

The compound that will accumulate is B.

Explanation:

Enzymes in any biochemical process are the protein molecules that speed up the rate of the biological reaction. It lowers down the activation energy of the reactant molecules.

Since from the question:

<u>A + E1 –> B + E2 –> C</u>

Given that A, B and C are the molecules in the pathway and E1 and E2 are the enzymes.

<u>This means that A undergoes some biological reaction in which E1 is acting a catalyst to give B and which further undergoing another biological reaction to give C in the presence of enzyme E2.</u>

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3 years ago
What mass of potassium hypochlorite (FW-90.6 g/mol) must be added to 4.50 x 10 mL of water to give a solution with pH 10.20? [Ka
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Answer : The mass of potassium hypochlorite is, 4.1 grams.

Explanation : Given,

pH = 10.20

Volume of water = 4.50\times 10^2ml=0.45L

The decomposition of KClO  will be :

KClO\rightarrow K^++ClO^-

Now the further reaction with water (H_2O) to give,

ClO^-+H_2O\rightarrow HClO+OH^-

First we have to calculate the pOH.

pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-10.20=3.8

Now we have to calculate the OH^- concentration.

pOH=-\log [OH^-]

3.8=-\log [OH^-]

[OH^-]=1.58\times 10^{-4}M

Now we have to calculate the base dissociation constant.

Formula used : K_b=\frac{K_w}{K_a}

Now put all the given values in this formula, we get :

K_b=\frac{1.0\times 10^{-14}}{4.0\times 10^{-8}}=2.5\times 10^{-7}

Now we have to calculate the concentration of ClO^-.

The equilibrium constant expression of the reaction  is:

K_b=\frac{[OH^-][HClO]}{[ClO^-]}

As we know that, [OH^-]=[HClO]=1.58\times 10^{-4}M

2.5\times 10^{-7}=\frac{(1.58\times 10^{-4})^2}{[ClO^-]}

[ClO^-]=0.0999M

Now we have to calculate the moles of ClO^-.

\text{Moles of }ClO^-=\text{Molarity of }ClO^-\times \text{Volume of solution}

\text{Moles of }ClO^-=0.0999mole/L\times 0.45L=0.0449mole

As we know that, the number of moles of ClO^- are equal to the number of moles of KClO.

So, the number of moles of KClO = 0.0449 mole

Now we have to calculate the mass of KClO.

\text{Mass of }KClO=\text{Moles of }KClO\times \text{Molar mass of }KClO

\text{Mass of }KClO=0.0449mole\times 90.6g/mole=4.07g\approx 4.1g

Therefore, the mass of potassium hypochlorite is, 4.1 grams.

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