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11Alexandr11 [23.1K]
3 years ago
6

Calculate the Ka for a 0.3 M solution of HA (unknown weak acid) if the pH = 3.65. The reaction can be modelled as HA (aq) + H2O

(l) ←→ A- (aq) + H3O+ (aq).
Chemistry
1 answer:
Levart [38]3 years ago
5 0

The Ka : 1.671 x 10⁻⁷

<h3>Further explanation</h3>

Given

Reaction

HA (aq) + H2O (l) ←→ A- (aq) + H3O+ (aq).

0.3 M HA

pH = 3.65

Required

Ka

Solution

pH = - log [H3O+]

\tt [H_3O^+]=10^{-3.65}=2.239\times 10^{-4}

ICE method :

HA (aq)        ←→   A- (aq)    +    H3O+ (aq).

0.3                           0                 0

2.239.10⁻⁴           2.239.10⁻⁴   2.239.10⁻⁴

0.3-2.239.10⁻⁴    2.239.10⁻⁴    2.239.10⁻⁴

\tt Ka=\dfrac{[H_3O^+][A^-]}{[HA]}\\\\Ka=\dfrac{(2.239.10^{-4}){^2}}{0.3-2.239.10^{-4}}\\\\Ka=1.671\times 10^{-7}

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Answer:

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Explanation:

The chemical reaction talks about the synthesis of calcium carbonate

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Let us write the equation of reaction as follows:

Na_2CO_{3(aq)}+CaCl_{2(aq)}\text{ }\rightarrow2NaCl_{(s)\text{ }}+CaCO_{3(aq)}

Firstly, we want to get the expected mass of calcium carbonate

This speaks about getting the theoretical yield based on the equation of reaction

From the data collected, 90 ml of 0.20 M (mol/L) of sodium carbonate gave calcium carbonate

We need to get the actual number of moles of sodium carbonate that reacted

We can get this by multiplying the volume by the molarity (kindly note that we have to convert the volume to Liters by dividing by 1000)

Thus, we have it as:

\frac{90}{1000}\times\text{ 0.1 = 0.009 moles}

Hence, we see that 0.009 moles of sodium carbonate reacted theoretically

Since 1 mole of sodium carbonate gave 1 mole calcium carbonate, it is expected that 0.009 mole of sodium carbonate will give 0.009mole of calcium carbonate

What we have to do now is to get the theoretical grams of calcium carbonate produced

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The theoretical yield (expected mass) is thus:

100\text{ g/ mol }\times\text{ 0.009mol = 0.9 g}

Finally, we proceed to get the percentage yield which is calculated using the formula below:

\text{Percent Yield = }\frac{Actual\text{ yield}}{\text{Theoretical yield}}\times\text{ 100 \%}

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Answer:

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<em>Note: The question is incomplete. The complete question is given below:</em>

<em>Ammonium perchlorate (NH₄ClO₄) is the solid rocket fuel used by the U.S. Space Shuttle. It reacts with itself to produce nitrogen gas (N₂) , chlorine gas (Cl₂), oxygen gas (O₂), water (H₂O) , and a great deal of energy. What mass of water is produced by the reaction of 9.6 g of ammonium perchlorate? Be sure your answer has the correct number of significant digits.</em>

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