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tamaranim1 [39]
3 years ago
6

What mass of solid sodium formate (of MW 68.01) must be added to 150 mL of 0.42 mol/L formic acid (HCOOH) to make a buffer solu-

tion having a pH of 3.74? Ka = 0.00018 for HCOOH.
Answer in units of g.
Chemistry
1 answer:
Sergio [31]3 years ago
4 0

Answer:

We need 4.28 grams of sodium formate

Explanation:

<u>Step 1:</u> Data given

MW of sodium formate = 68.01 g/mol

Volume of 0.42 mol/L formic acid = 150 mL = 0.150 L

pH = 3.74

Ka = 0.00018

<u>Step 2:</u> Calculate [base)

3.74 = -log(0.00018) + log [base]/[acid]

0 = log [base]/[acid]

0 = log [base] / 0.42

10^0 = 1 = [base]/0.42 M

[base] = 0.42 M

<u>Step 3:</u> Calculate moles of sodium formate:

Moles sodium formate = molarity * volume

Moles of sodium formate = 0.42 M * 0.150 L = 0.063 moles

<u>Step 4:</u> Calculate mass of sodium formate:

Mass sodium formate = moles sodium formate * Molar mass sodium formate

Mass sodium formate = 0.063 mol * 68.01 g/mol

Mass sodium formate = 4.28 grams

We need 4.28 grams of sodium formate

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The pH of a solution which is 0.023 m in weak base and 0 037 m in the conjugate weak acid whose Ka= 7.1 × 10⁻⁶ is 4.93.

pH determines the amount of hydrogen and hydroxide ions in a solution. It is the negative logarithm of hydrogen ion concentration.

Given,

Ka= 7.1 × 10⁻⁶

Weak base = 0.023M

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Using base dissociation constant, Ka we can calculate pKa by:

pKa = -log [Ka]

pKa = -log [7.1 × 10⁻⁶]

pKa = 5.15

A weak base and its conjugate acid are present in equal proportions in buffer solution. Using the Henderson-Hasselbalch equation, we can find out the pH of a buffer solution that constitutes a weak base and its conjugate acid.

Using Henderson-Hasselbalch equation,

pH = pKa + log [Weak base / acid]

pH = 5.15 + log [0.023 / 0.037]

pH = 5.15 + log[0.6]

pH = 5.15 - 0.22

pH = 4.93

Therefore, the pH of the solution is 4.93.

Learn more about pH here, brainly.com/question/22390063

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5 0
1 year ago
The diagram below shows the PH values of several substances.
skelet666 [1.2K]

Answer:

Changes in colour of litmus paper.

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PH values:-

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K is acidic as pH is <7

Hence K will change the colour of blue litmus paper.

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Examples of substances

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Explanation:

The wavelength of the photon that is emitted from the atom during the transition depends on the transition from different states. If the photon is emitted from n=4 state to n=3 state, the wavelength of photon is 1875 while on the other hand, if the photon is emitted from n=5 state to n=3 state, the wavelength of photon is 1282. If the photon is emitted from n=3 state to n=2 state, the wavelength of photon is 656.

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Dalton theorized that matter is made of tiny, indivisible particles called atoms. In what way did the theories of each
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7 0
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Need help with science pls help me
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Answer:

B. negative charge only

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