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11 Dec 2019

Using the following information, calculate the number of moles of HCl, Moles of Borate, Concentration of Borate, Ksp, Average Ksp, ΔG (kJ/mol), ΔH (kJ/mol), and ΔS (J/mol*K):

Na2B4O7 • 10H2O(s) -><- 2Na+(aq) + B4O5(OH)42−(aq) + 8H2O(l)

Titration: B4O5(OH)42-(aq) + 2HCl(aq) + 3H2O(l) → 4 B(OH)3(aq) + 2 Cl− (aq)

Molar Mass of B: 10.81g/mol, Molar Mass of O: 16.00g/mol, Molar Mass of H: 1.008g/mol, Molar Mass of Cl: 35.45g/mol

K = [Na+]2 [B4O5(OH)42-]

Ksp = 4 [B4O5(OH)42-]3

ΔG = −RT ln Ksp

ΔG = ΔH – TΔS

−RT ln Ksp = = ΔH – TΔS

a)Titration 1: Temperature: 28.0 degrees C, Concentration of HCl: 0.251 M, Volume of Borax solution (mL): 5.00, Volume of HCl titrated: 2.00 mL

Please do not post the lab that this question comes from because it is hard for me to understand. Please show each individual step and use units along the way to the answer. Thanks!

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Related questions

Postlab Help- these are all the questions I need to answer (data at bottom). This was a titration lab where a saturated solution of borax was prepared by adding 25.0 g of borax to 50 mL of distilled water. We used two different temperatures by using a hot plate to heat the solution. After the solid settled, we took 5.0 mL of the decant on top and put it into a graduated cylinder. After this we titrated it with 100 mL of HCl:

Analysis

A1. Determine the concentration of the dissolved B4O5(OH)42– in each sample titrated; show a complete calculation for beaker #1.

A2. Calculate Ksp for each borax solution.

A3. Prepare a graph of your results, plotting the two quantities x and y (as defined in the introduction). Label everything clearly! Draw a best fitted line.

A4. Using y=mx+b of your best fitted line, calculate DH° and DS° for this reaction. Make sure to keep track of units, especially for R, so that the units of DH° and DS° work out sensibly.

Post Lab Questions:

Q1) What would happen to experimental Ksp if the buret was contaminated with other acids?

Summary :

Solubility of borax (make sure to indicate the unit and condition) :

Ksp (one or many? What makes sense?) :

Include graph (site the page). Include all relevant information directly on the graph.

Experimental DH° in kJ/mol :

Theoretical DH° in kJ/mol :

Experimental DS° in J/mol K :

Theoretical DS° in J/mol K :

Trial Initial Volume (mL) Change in Volume (mL) Final Volume (mL) Temperature (oC) Volume decant (mL)
1 0.3 10.6 10.9 24.0 5.0
2 10.9 15.9 26.8 30.5 5.0

The calorimeter above was used to determine the enthalpy of the reaction between hydrochloric acid and sodium hydroxide. The relevant temperatures at the time of reaction (assuming the reaction was instantaneous) were determined as above. Temperatures were recorded as a function of time and extrapolated to the time of mixing. The generic graph is shown below. The temperature axis is again intentionally not displayed. The relevant information is given in the table below.



The data for the reaction between HCl and NaOH were as follows:

Value Units
Concentration of HCl 2.45 M
Volume of HCl 50.0 mL
Density of HCl 1.02 g/mL
Concentration of NaOH 2.39 M
Volume of NaOH 55.0 mL
Density of NaOH 1.02 g/mL
Specific Heat of HCl & & NaOH & Reaction Mixture 3.97 J/g-K
Temperature of HCl at 3.0 min, Tacid (from graph) 25.4 oC
Temperature of NaOH at 3.0 min, Tbase (from graph) 25 oC
Temperature of reaction mixture at 3.0 min, Tmix (from graph) 40.7 oC

If the temperatures of the acid and base at the time of mixing are different, use their average as the temperature of the mixture before reaction. Use the average also as the initial temperature of the calorimeter.

What is the weight of the reaction solution in grams?

107.1 Correct

the change in temperature experienced by the reaction mixture (and the calorimeter) extrapolated back to the time of mixing?

15.5 Correct

What is the molar enthalpy, ΔHneut, of the reaction in:

H+ (aq) + OH- (aq) → H2O (l)

in kJ/mol?

-57.3

Question:

The above experiment is repeated using the weak monoprotic acid, crotonic acid, in place of hydrochloric acid. The molar enthalpy of the reaction between the crotonic acid and sodium hydroxide, ΔHweak is determined to be -51.3 kJ/mol. Using Hess' Law and your result for HCl, what is the enthalpy of dissociation of crotonic acid in kJ/mol?

This is for the lab practical I take on Tuesday night. If you could answer each one and show your work/ explain that'd be amazing so I can do well on the actual practical on Tuesday! Thank you!

Chemistry 211 Lab Final Study Guide Spring 2015

Useful Information:
1 ampere =coulomb/sec
Faraday’s constant = 96,500 coulombs/mole of electrons
Molar mass of Au = 197.0 g/mole, Molar mass of Cu = 63.55 g/mole
m = moles , ' ’

c kg

ΔTf

= Tf

− Tf

where Tf is for the pure solvent and Tf

is for the mixture.

ΔT = (K

)(m ) ,

m = (

(mass of

solute, g )
)( ).

f f c

c molar

mass, g

mol −1

mass of

solvent, kg


7. Next question

(a) If you weigh 6.355 grams of copper, add concentrated nitric acid to dissolve it, and then dilute the solution to a total volume of 50 mL, how many moles of copper are in this solution?


(b) For the equilibrium reaction 3H2(g) + N2(g) → 2NH3(g), what is the equilibrium constant expression, Kc, for this reaction? (5pts)

8. Suppose at some temperature, the equilibrium concentration of H2 is 0.45M, the equilibrium concentration of N2 is 0.38M, and the equilibrium concentration of NH3 is 0.42M. What is the value of the equilibrium constant for the reaction 3H2(g) + N2(g) → 2NH3(g) at this temperature? (Show your work. No credit will be given if your work is not shown.)

9. Next question
(a) If you need 0.0534 moles of NaOH to reach equivalent point in the titration with acetic acid, how many mL of 0.09876M NaOH will you need?


(b) The Ksp of Cu(OH)2 is 2.2x10-20, what is the solubility of Cu(OH)2?


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(a) In non-sulfide qualitative analysis of representative cations, the Group A cations comprising of Pb2+,

Hg2+, and Ag+ give a precipitate with solution.
(b) From a solution containing mixture of Pb2+, Fe3+, and Al3+, Pb2+ is removed by adding HCl solution. To the remaining cation mixture, on making the solution basic with NH3 (pH=9 – 10), both the cations form precipitate. Further analysis of the cation mixture containing Fe3+ and Al3+ is carried out by adding NaOH solution.


Aluminum hydroxide (dissolves/remains undissolved) in NaOH solution while Ferric hydroxide ( dissolves/remains undissolved).
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