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Svetach [21]
3 years ago
8

(30 Points) You need to produce a buffer solution that has a pH of 5.02. You already have a solution that contains 10. mmol (mil

limoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution? The pKa of acetic acid is 4.74. Express your answer numerically in millimoles.
Chemistry
2 answers:
chubhunter [2.5K]3 years ago
8 0
<span>By definition:

pH = pKa + log [acetate]/ [acetic acid]

so

5.02 = 4.74 + log [acetate] / 10 mmole

10mmole = 10/1000 = 0.01 mole

5.02 = 4.74 + log [acetate] / 0.01

5.02 - 4.74 = 0.28 = log [acetate] /0.01


10^0.28 = </span><span>1.90546</span> = [acetate] / 0.01 <span>
[acetate] = 0.019 mole 

= 19 millimoles

</span>
ElenaW [278]3 years ago
3 0
<span>pH = pKa + log [acetate]/ [acetic acid] ( Handerso-Hasselbalch equation)

5.35 = 4.74 + log acetate / 0.010 moles

5.35 - 4.74 =0.61 = log acetate / 0.010

10^0.61 =4.1 = acetate / 0.010

moles acetate = 0.041

millimoles acetate required = 41</span>
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Consider the Gibbs energies at 25 ∘C.
zysi [14]

Answer:

A)Δ​G​r​x​n​∘​=​55.7​k​J​/​m​o​l

B)Ksp=1.75×10^−10

C)Δ​G​r​x​n​∘​=​70.0​k​J​/​m​o​l

D)Ksp=5.45×10^−13

Explanation:

ΔGrxn∘=​Δ​G​f​,​p​r​o​d​u​c​t​s​∘​−​Δ​G​f​,​r​e​a​c​t​a​n​t​s​∘

To calculate for the

Ksp

of the dissolution reaction can be claculated

ΔGrxn∘=−RTlnKsp

where R is the proportionality constant equal to 8.3145 J/molK.

A)

Δ​G​r​x​n​∘​=​[​Δ​G​f​,​A​g​(​a​q​)​+​∘​+​Δ​G​f​,​C​l​(​a​q​)​−​∘​]​−​Δ​G​f​,

A​g​C​l​(​s​)​⇌​A​g​(​a​q​)​+​+​C​l​(​a​q​)​−

ΔG∘rxn=[77.1kJ/mol+(−131.2kJ/mol)]−(−109.8kJ/mol)

Δ​G​r​x​n​∘​=​55.7​k​J​/​m​o​l

b) Calculate the solubility-product constant of AgCI.

ΔGrxn∘=−RTlnKsp

55.7​k​J​/​m​o​l​=​−​(​8.3145​×​10​−​3​J​/​m​o​l​K​)​(​298.15​K)InKsp

Ksp=1.75×10^−10

c) Calculate

To calculate ΔG°rxn

for the dissolution of AgBr(s).

Δ​G​r​x​n​∘​=​[​Δ​G​f​,​A​g​(​a​q​)​+​∘​+​Δ​G​f​,​B​r​(​a​q​)​−​∘​]​−​Δ​G​f​,

Δ​G​r​x​n​∘​=​[​77.1​k​J​/​m​o​l​+​(​−​104.0​k​J​/​m​o​l​)​]​−​(​−96.90kj/mol

Δ​G​r​x​n​∘​=​70.0​k​J​/​m​o​l

d)To Calculate the solubility-product constant of AgBr.

ΔGrxn∘=−RTlnKsp

70.0kJ/mol=−(8.3145×10−3J/molK)(298.15K)lnKsp

70.0​k​J​/​m​o​l​=​−​(​8.3145​×​10​−​3​J​/​m​o​l​K​)​(​298.15​K

Ksp=5.45×10^−13

8 0
3 years ago
3.364 g of hydrated barium chloride of BaCL2.xH2O was dissolved in water and made up to a total volume of 250.0 mL. 10.00 mL of
atroni [7]

<u>Given:</u>

Mass of hydrated barium chloride = 3.364 g

Total volume of barium chloride V(total)= 250 ml

Volume taken for titration V = 10 ml

Volume of AgNO3 consumed = 46.92 ml

Concentration of AgNO3 = 0.0253 M

<u>To determine:</u>

The value of x i.e. the water of hydration in BaCl2

<u>Explanation:</u>

The net ionic equation is-

Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

Based on the reaction stoichiometry: Equal moles of Ag+ and Cl- combine to form AgCl

Moles of Ag+ consumed = moles of Cl- present

Moles of Ag+ = V(AgNO3) * M(AgNO3) = 0.04692 * 0.0253 = 0.00119moles

Moles of Cl- present = 0.00119 moles

Thus, 0.00119 moles of Cl- are present in 10 ml of the solution

Therefore, number of moles of Cl- in 250 ml would be-

= 0.00119 * 250 /10 = 0.02975 moles of cl-

Now:

2 moles of Cl- are present in 1 mole of BaCl2

Therefore, 0.02975 moles of Cl- correspond to- 0.02975 * 1/2 = 0.01488 moles of BaCl2

Molar mass of BaCl2 = 208.22 g/mol

Thus, mass of BaCl2 = 0.01488 moles * 208.22 g.mol-1 = 3.098 g

Mass of water of hydration = 3.364 - 3.098 = 0.266 g

# moles of water 'x' = .266/18 = 0.015 ≅ 1

Ans: Formula for hydrated barium chloride = BaCl2. 1H2O



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How many zeroes in 0.0079 are significant digits
sergejj [24]

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The 2 zeros after the decimal point

6 0
4 years ago
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What is the mass of naoh that would have to be added to 500 ml of a solution of 0.20 m acetic acid in order to achieve a ph of 5
il63 [147K]

The correct answer is 2.5 g.

Let x be the mass of NaOH in grams

The molar mass of NaOH = 40.0 gms/mol

Moles of NaOH = mass / molecular mass of NaOH

= x grams / 40.0 gms /mol = 0.025 x mol

Initial moles of CH₃COOH = volume × concentration of CH₃COOH

= 500 / 1000 × 0.20 = 0.1 mol

CH₃COOH + NaOH ⇒ CH₃COONa + H2O

Moles of CH₃COOH left = initial moles of CH₃COOH - moles of NaOH = 0.1 - 0.025x mol

Moles of CH₃COONa formed = moles of NaOH = 0.025x mol

Henderson-Hasselbalch equation:

pH = pKa + log ([CH₃COONa] / [CH₃COOH])

= pKa + log (moles of CH₃COONa /moles of CH₃COOH)

5.0 = 4.76 + log [0.025a / (0.1 - 0.025a)]

log [0.025a / (0.1 - 0.025a)] = 0.24

0.025a / (0.1 - 0.025a) = 10^0.24 = 1.738

0.068445a = 0.17378

a = 0.17378 / 0.068445

= 2.54 g

Mass of NaOH = a = 2.54 g or 2.5 g

4 0
3 years ago
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