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satela [25.4K]
3 years ago
5

Write a mechanism for the esterification of propanoic acid with 18O-labeled ethanol. Show clearly the fate of the 18O label. (b)

Acid-catalyzed hydrolysis of an unlabeled ester with 18O-labeled water (H218O) leads to incorporation of some 18O into both oxygens of the carboxylic acid product. Explain by a mechanism. (Hint: You must use the fact that all steps in the mechanism are reversible.)
Chemistry
1 answer:
tatuchka [14]3 years ago
5 0

Answer:

See explanation and images attached

Explanation:

a) In the mechanism for the acid catalysed esterification of propanoic acid using ethanol, we can see that the first step is the protonation of the acid followed by nucleophillic attack of the alcohol. Loss of water and consequent deprotonation regenerates the acid catalyst. We can see the fate of the 18O labelled ethanol in the mechanism shown.

b)  In the second mechanism, an unnamed ester is hydrolysed using an acid catalyst. The attack of the acid and subsequent nucleophillic attack of water labelled with 18O leads to the incorporation of this 18O into the product acid as shown in the mechanism attached to this answer.

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What must be the molarity of an aqueous solution of trimethylamine, (ch3)3n, if it has a ph = 11.20? (ch3)3n+h2o⇌(ch3)3nh++oh−kb
Stolb23 [73]

0.040 mol / dm³. (2 sig. fig.)

<h3>Explanation</h3>

(\text{CH}_3)_3\text{N} in this question acts as a weak base. As seen in the equation in the question, (\text{CH}_3)_3\text{N} produces \text{OH}^{-} rather than \text{H}^{+} when it dissolves in water. The concentration of \text{OH}^{-} will likely be more useful than that of \text{H}^{+} for the calculations here.

Finding the value of [\text{OH}^{-}] from pH:

Assume that \text{pK}_w = 14,

\begin{array}{ll}\text{pOH} = \text{pK}_w - \text{pH} \\ \phantom{\text{pOH}} = 14 - 11.20 &\text{True only under room temperature where }\text{pK}_w = 14 \\\phantom{\text{pOH}}= 2.80\end{array}.

[\text{OH}^{-}] =10^{-\text{pOH}} =10^{-2.80} = 1.59\;\text{mol}\cdot\text{dm}^{-3}.

Solve for [(\text{CH}_3)_3\text{N}]_\text{initial}:

\dfrac{[\text{OH}^{-}]_\text{equilibrium}\cdot[(\text{CH}_3)_3\text{NH}^{+}]_\text{equilibrium}}{[(\text{CH}_3)_3\text{N}]_\text{equilibrium}} = \text{K}_b = 1.58\times 10^{-3}

Note that water isn't part of this expression.

The value of Kb is quite small. The change in (\text{CH}_3)_3\text{N} is nearly negligible once it dissolves. In other words,

[(\text{CH}_3)_3\text{N}]_\text{initial} = [(\text{CH}_3)_3\text{N}]_\text{final}.

Also, for each mole of \text{OH}^{-} produced, one mole of (\text{CH}_3)_3\text{NH}^{+} was also produced. The solution started with a small amount of either species. As a result,

[(\text{CH}_3)_3\text{NH}^{+}] = [\text{OH}^{-}] = 10^{-2.80} = 1.58\times 10^{-3}\;\text{mol}\cdot\text{dm}^{-3}.

\dfrac{[\text{OH}^{-}]_\text{equilibrium}\cdot[(\text{CH}_3)_3\text{NH}^{+}]_\text{equilibrium}}{[(\text{CH}_3)_3\text{N}]_\textbf{initial}} = \text{K}_b = 1.58\times 10^{-3},

[(\text{CH}_3)_3\text{N}]_\textbf{initial} =\dfrac{[\text{OH}^{-}]_\text{equilibrium}\cdot[(\text{CH}_3)_3\text{NH}^{+}]_\text{equilibrium}}{\text{K}_b},

[(\text{CH}_3)_3\text{N}]_\text{initial} =\dfrac{(1.58\times10^{-3})^{2}}{6.3\times10^{-5}} = 0.040\;\text{mol}\cdot\text{dm}^{-3}.

8 0
3 years ago
What volume would 0.853 moles of Nitrogen gas occupy at STP?
beks73 [17]

Answer:

19.12 L

Explanation:

At STP(i.e. Standard temperature and pressure).

The volume occupied by one mole of gas = 22.4 L

The pressure = 1 atm

The temperature = 273 K

Thus, since 1 mole of gas = 22.4 L;

Then 0.853 moles of N2 gas will occupy:

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= 19.12 L

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Consider the reaction below:
melisa1 [442]

Answer:

(A) first order reaction

Explanation:

A first order reaction is a type of reaction in which the rate of the reaction depends only on the concentration on one of the reactants. Since A is the only reactant we have, it is right to deduce that this reaction is a first order reaction.

Note: while the order of this reaction is 1, its molecularity is 2. The molecularity of a reaction is the number of moles of reactants that is actually reacting.

(B) is wrong

This is because a zero order reaction is one in which the rate of reaction is not influenced by the concentrations of the reactants and hence remains constant irrespective. Since we were not furnished with this idea in the question, it is only right that we reject this answer.

(C) is wrong.

C is outrightly wrong as we have only one reactant.

(D) is wrong

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• Balance this chemical equation.
user100 [1]

Answer:

Explanation:

Chemical equation:

FeCl₃  +  NaOH   →  Fe(OH)₃ + NaCl

Balanced chemical equation:

FeCl₃  +  3NaOH   →  Fe(OH)₃ + 3NaCl

Step 1:

FeCl₃  +  NaOH   →  Fe(OH)₃ + NaCl

Fe = 1                             Fe = 1

Cl =  3                            Cl = 1

Na =  1                            Na =  1

OH = 1                             OH = 3

Step 2:

FeCl₃  +  3NaOH   →  Fe(OH)₃ + NaCl

Fe = 1                              Fe = 1

Cl =  3                             Cl = 1

Na =  3                            Na =  1

OH = 3                             OH = 3

Step 3:

FeCl₃  +  3NaOH   →  Fe(OH)₃ + 3NaCl

Fe = 1                              Fe = 1

Cl =  3                             Cl = 3

Na =  3                            Na =  3

OH = 3                             OH = 3

Now we the equation is completely balanced and follow  the law of conservation of mass because there are equal number of atoms of each elements are present on both side.

According to the law of conservation mass, mass can neither be created nor destroyed in a chemical equation.

This law was given by french chemist  Antoine Lavoisier in 1789. According to this law mass of reactant and mass of product must be equal, because masses are not created or destroyed in a chemical reaction .

Type of reaction:

It is double displacement reaction.

Double replacement:

It is the reaction in which two compound exchange their ions and form new compounds.

AB + CD → AC +BD

4 0
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