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Dinesh Singh

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I am graduate from luckhnow university and after that I am working as chemistry full time teacher in reputed organisation.

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Numerade tutor for 5 years
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Unlocking the Power of Thermodynamics: A Comprehensive Guide

Dinesh's Textbook Answer Videos

1

Dinesh's Quick Ask Videos

01:10
Chemistry 101

DOE Minitab. You are a consultant in the design of experiments for a chemical process company. One of the processes requires reaching and maintaining the temperature at which one of the company's processes is carried out, between 600 and 700 °F. To achieve this objective, the appropriate combination of five variables that affect temperature must be achieved: MgBr concentration (A); Oxygen rate (B); Nitrogen level (C); Ionization rate (D); and concentration of NaCl2 (E).

To achieve the desired combination, you propose to carry out three runs of a 2^5 factorial design. Since your proposal would entail a high cost for the company, you are authorized to carry out a 2^5-1 design with two replicates. The results are the following:

Factors
Temperature
A
B
C
D
E
Replica 1
Replica 2
Treatment
MgBr
Oxygen
Nitrogen
Ionization
NaCl2
Y1
Y2
1
20
1
200
5
0.9
765.9
768.7
2
20
1
200
10
0.1
243.6
234.1
3
20
1
500
5
0.1
495.1
593.5
4
20
1
500
10
0.9
518.3
456.4
5
20
10
200
5
0.1
505.4
522.9
6
20
10
200
10
0.9
487.9
498.6
7
20
10
500
5
0.9
768.0
702.8
8
20
10
500
10
0.1
296.7
271.7
9
80
1
200
5
0.1
635.3
622.8
10
80
1
200
10
0.9
387.0
380.9
11
80
1
500
5
0.9
676.3
680.0
12
80
1
500
10
0.1
366.1
325.4
13
80
10
200
5
0.9
640.1
650.7
14
80
10
200
10
0.1
357.3
347.2
15
80
10
500
5
0.1
526.8
527.4
16
80
10
500
10
0.9
419.9
411.0

a) Estimate the effects of the factors. What effects appear to be great?
b) Perform the analysis of variance to confirm your conclusions for part (a).
c) What is the equation to predict the temperature based on the results of this experiment? How good is this model? (hint: check model assumptions)
d) What levels of the factors (both significant and non-significant, if any) included in your model would you recommend using to achieve the objective? (hint: perform optimization)

01:04
Chemistry 101

Create a schematic diagram on how to prepare a Phosphate Buffer
NaH2PO4 - K2HPO4 with a final volume of 500 ml, concentration of
0.10 M with a pH of 7.20 from 0.20 M NaH2PO4 and solid K2HPO4. Note:
K = -6.3 x 10^8. Reminders: Show all calculations before preparing the
schematic diagram. For solid K2HPO4, calculate the mass (based
on calculated moles of salt) rather than the volume since this is
a solid substance. Calculations (20 pts): Schematic Diagram (20
pts): Additional Question (10 pts): What is the change in pH if
1.50 ml of 1.00 M HCl is added to the buffer solution? Is the buffer
effective? Show your calculation.

04:08
Chemistry 101

If the [H+] is 2.1 × 10^(-12) M HClO4, what is the pH?
Is the solution ACIDIC, BASIC, or NEUTRAL?
Calculate the pOH if the [OH-] concentration is 5.9 × 10^(-1) M? Is the solution ACIDIC, BASIC, or NEUTRAL?
What is the pH of a 0.033 M KOH solution?
What is the pH of an aqueous solution with a hydroxide ion concentration of 1.8 × 10^(-3) M?
What is the pH of an aqueous solution with a hydroxide ion concentration of 1.2 × 10^(-6) M?
What is the hydrogen ion concentration of a solution with a pH = 8.25?
What is the pH of a 0.235 M Ba(OH)2 solution?
What is the pH of a solution of pure water at 30°C?
The Ka of a weak acid, HA, is 1.6 × 10^(-6). What is the pH of the solution?
12. What is the hydroxide ion concentration in an aqueous solution with a hydrogen ion concentration of 2.70 × 10^(-2) M?
Calculate the pH of a solution that is 0.147 M HCl?

03:33
Chemistry 101

A 100 mL buffer solution containing 0.0500 M H2SO3 and 0.100 M Na2SO3 will be titrated with 0.100 M NaOH.

a) Calculate the initial pH of this solution.
b) What is the pH of the solution at the first end point?
c) Find out the pH at the second end point.
d) Suggest one indicator for each of the end points. What will be the color changes at these end points?

For H2SO3:
Ka1 = 1.23 x 10^2
Ka2 = 6.6 x 10^8

02:08
Chemistry 101

* The pH of a sodium benzoate (C6H5COONa) solution is 9.00. What is C6H5COONa? (Ka = 6.0 x 10^-5 for C6H5COOH acid)
* a) What are the concentrations of H+(aq), OCl-(aq), and HOCl(aq) in a 0.20 M HOCl solution? b) What is the ionization percentage of HOCl in this solution? (Ka = 3.2 x 10^-8 for HOCl)
* C2H4(g) + H2(g) -> C2H6(g) The activation energy of the reaction is 181 kJ/mol and the value of the rate constant k at 700 K is 1.3 x 10^-3 L/mol.s. What is the rate constant value (k) of this reaction at 730 K? (R = 8.314 J/mol.K)
* Compare the acidity of H2S, H2Se, and H2Te. How does acidity vary between the hydrides of a group of elements?
* Explain how to prepare a 750 mL 0.125 M CaCl2 solution using 89% pure solid (MCaCl2 = 111 g/mol).
* Cocaine (K) is a weak base and its ionization in water is as follows: K(aq) + OH-(aq) -> 5.0 x 10^-3 M. Since the pH of the cocaine solution is 10.04, what is the ionization constant of this substance?
* At 25°C, 1 liter of water dissolves 1.7 x 10^-5 mol Cd(OH)2. Calculate the Ksp value of Cd(OH)2.
* Diphosphorus tetraiodide is obtained by the reaction P4O6 + 4I2 -> 2P2I4 + P4O10. a) How many grams increase from each reagent? b) How many grams of P2I4 are formed? (P = 30.97 g/mol, O = 16 g/mol, I = 126.90 g/mol)
* Find a) molarity and b) molality since the density of a 15% AgNO3 solution by mass is 1.08 g/mL. (AgNO3: 170 g/mol)
* A solution containing 20.0 grams of a substance dissolved in exactly 1 mole of a volatile solvent has a vapor pressure of 0.500 atm at 20°C. If 1 mole more than the solvent is added to the mixture, the vapor pressure of the resulting solution at the same temperature is 0.550 atm. a) What is the molecular weight of the solute? b) What is the vapor pressure of a pure solvent at 20°C?

02:06
Chemistry 101

(a) A student mixed 200 mL of 0.15 M ammonium chloride, NH4Cl, with 200 mL of 0.23 M ammonia solution, NH3.
i) Calculate the pH value of the mixture.
ii) Calculate the concentrations of OH- in the mixture. [Kb for NH3 = 1.8 x 10^-5]
(b) Consider a titration between HNO3 and NH3.
i) Write the reaction equation for this titration.
ii) Sketch the titration curve if the burette contains NH3 and the conical flask contains HNO3.
iii) Classify the salt as neutral, acidic, or basic.

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