Photometric analysis of trace amounts of hydrazine with p-dimethylamino benzaldehyde. Chemical equilibria. Part II

1968 ◽  
Vol 46 (8) ◽  
pp. 1365-1371 ◽  
Author(s):  
Donald S. Gamble
Keyword(s):  
Aqueous Solutions ◽  
Equilibrium Constant ◽  
Chemical Equilibrium ◽  
Experimental Error ◽  
Photometric Measurement ◽  
Hydrazine Sulfate ◽  
Photometric Analysis ◽  
Thermodynamic Equilibrium Constant ◽  
Chemical Equilibria ◽  
Equilibrium Data

Additional chemical equilibrium data are presented for aqueous solutions into which have been put p-dimethylaminobenzaldehyde, HCl, and hydrazine sulfate. The photometric measurement of the thermodynamic equilibrium constant for p-dimethylaminobenzaldehyde protonation agrees to within experimental error with the value from solubility experiments. The average of the two is [Formula: see text].Some analytical chemical applications are discussed.

scholarly journals Generalized Chemical Equilibrium Constant of Formaldehyde Oligomerization

2021 ◽  
Author(s):  
Raphael Kircher ◽  
Niklas Schmitz ◽  
Jürgen Berje ◽  
Kerstin Münnemann ◽  
Werner R. Thiel ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Equilibrium Constant ◽  
Chemical Equilibrium ◽  
Equilibrium Constants ◽  
13C Nmr Spectroscopy ◽  
Hydroxyl Groups ◽  
Chemical Equilibria ◽  
Collective Data ◽  
Generalized Equilibrium ◽  
Novel Method

Formaldehyde reacts with solvents that contain hydroxyl groups (R–OH) in oligomerization reactions to oxymethylene oligomers (R–(OCH2)n–OH). The chemical equilibria of these reactions have been studied in the literature for water, for the mono-alcohols methanol, ethanol, and 1-butanol, as well as for the diols ethylene glycol and 1,4-butynediol. In the present work, the collective data were analyzed. It was found that the prolongation of the oxymethylene chains by the addition of formaldehyde can be described very well with a generalized chemical equilibrium constant Kx,n≥2R–OH, which is independent of the substructure (R) of the solvent. This holds for the oligomerization reactions leading to R–(OCH2)n–OH with n ≥ 2. The chemical equilibrium constant Kx,1R–OH of the reaction of formaldehyde with the solvent R–OH depends on the solvent, but simple trends are observed. The hypotheses of the existence of a generalized chemical equilibrium constant Kx,n≥2R–OH was tested for the reactions of formaldehyde with ethanol and 1-propanol, for which neither Kx,1R–OH nor Kx,nR–OH was previously available. The corresponding equilibria were studied by 13C NMR spectroscopy and the equilibrium constants were determined. A novel method was developed and used in these studies to obtain data on Kx,1R–OH by NMR spectroscopy, which is difficult because of the low amount of molecular formaldehyde. It was found that the generalized equilibrium constant is even valid for the acid-catalyzed formation of poly(oxymethylene) dimethyl ethers (OME).

Chemical Equilibrium

2009 ◽  
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Equilibrium Constant ◽  
Chemical Equilibrium ◽  
Cold Water ◽  
Reverse Reaction ◽  
Mass Action ◽  
Forward Reaction ◽  
Chemical Equilibria ◽  
Partial Pressures ◽  
The Relationship ◽  
Dynamic Equilibria

Many chemical reactions go to completion; i.e., all the reactants are converted to products. A good example is the reaction of calcium with cold water. . . Ca(s)+2 H2O(l) → Ca(OH)2(s)+ H2(g) . . . There is no evidence that the reverse reaction occurs. Such reactions are said to be irreversible. On the other hand, many reactions are reversible: the process can be made to go in the opposite direction. This means that both the reactants and products will be present at any given time. A reversible reaction is defined as one in which the products formed can react to give the original reactants. A double arrow is used to indicate that the reaction is reversible, as illustrated by the general equation:. . . aA+bB ⇌ cC +dD. . . At the start of the reaction, the reactants convert more quickly to products than products turn back to reactants because the reactants are present in much greater amount. Eventually the concentration of products is sufficient for the reverse reaction to become significant. The reaction is said to reach equilibrium when the net change in the products and reactants is zero, i.e., the rate of forward reaction equals the rate of reverse reaction. Chemical equilibria are dynamic equilibria because, although nothing appears to be happening, opposing reactions are occurring at the same rate. Figure 17-1 illustrates that for a reaction in chemical equilibrium, the rate of forward reaction equals the rate of reverse reaction. When a chemical reaction is at equilibrium, the concentrations of reactants and products are constant. The relationship between the concentrations of reactants and products is given by the equilibrium expression, also known as the law of mass action. For the general reaction:. . . aA+bB cC +dD. . . at a constant temperature, the equilibrium constant expression is written as: Kc = [C]c[D]d/[A]a[B]b where [A], [B], [C], and [D] are the molar concentrations or partial pressures of A,B,C, and D at equilibrium. The exponents a,b, c, and d in the equilibrium expression are the coefficients in the balanced equation; Kc is the equilibrium constant and is not given units. The subscript c shows that K is in terms of concentration. The numerical value for Kc is usually determined experimentally.

Photometric analysis of trace amounts of hydrazine with p-dimethylaminobenzaldehyde. Chemical equilibria

1967 ◽  
Vol 45 (22) ◽  
pp. 2813-2819 ◽  
Author(s):  
Donald S. Gamble ◽  
I. Hoffman
Keyword(s):  
Acid Solutions ◽  
Photometric Analysis ◽  
Dimethylamino Group ◽  
Chemical Equilibria ◽  
Aqueous Acid ◽  
Equilibrium Data ◽  
Equilibrium Scheme ◽  
Absorbance Peak

An equilibrium scheme is proposed for aqueous acid solutions containing hydrazine, p-di-methylaminobenzaldehyde and p-dimethylaminobenzaldazine. The quinoidal cation form of the latter has an absorbance peak at 455 mμ, for which [Formula: see text] (±2.1%). In 0.4 m to 1 m H+, 10−5 m benzaldazine is practically all in the quinoidal cation form. The acid attenuation of absorbance at 455 mμ is caused by protonation of the dimethylamino group of unreacted aldehyde. Semiquantitative equilibrium data are presented for the reaction between hydrazine and p-dimethylaminobenzaldehyde.

Comparison of the fixation of several metal ions onto a low-cost biopolymer

2002 ◽  
Vol 2 (5-6) ◽  
pp. 217-224 ◽  
Author(s):  
Z. Reddad ◽  
C. Gérente ◽  
Y. Andrès ◽  
P. Le Cloirec
Keyword(s):  
Aqueous Solutions ◽  
Metal Ions ◽  
Low Cost ◽  
Operating Conditions ◽  
Order Kinetic ◽  
Adsorption Mechanisms ◽  
Equilibrium Data ◽  
Order Kinetic Model ◽  
Beet Pulp ◽  
Removal Of Metal Ions

In the present work, sugar beet pulp, a common waste from the sugar refining industry, was studied in the removal of metal ions from aqueous solutions. The ability of this cheap biopolymer to sorb several metals namely Pb2+, Cu2+, Zn2+, Cd2+ and Ni2+ in aqueous solutions was investigated. The metal fixation capacities of the sorbent were determined according to operating conditions and the fixation mechanisms were identified. The biopolymer has shown high elimination rates and interesting metal fixation capacities. A pseudo-second-order kinetic model was tested to investigate the adsorption mechanisms. The kinetic parameters of the model were calculated and discussed. For 8 × 10-4 M initial metal concentration, the initial sorption rates (v0) ranged from 0.063 mmol.g-1.min-1 for Pb2+ to 0.275 mmol.g-1.min-1 for Ni2+ ions, with the order: Ni2+ > Cd2+ > Zn2+ > Cu2+ > Pb2+. The equilibrium data fitted well with the Langmuir model and showed the following affinity order of the material: Pb2+ > Cu2+ > Zn2+ > Cd2+ > Ni2+. Then, the kinetic and equilibrium parameters calculated qm and v0 were tentatively correlated to the properties of the metals. Finally, equilibrium experiments in multimetallic systems were performed to study the competition of the fixation of Pb2+, Zn2+ and Ni2+ cations. In all cases, the metal fixation onto the biopolymer was found to be favourable in multicomponent systems. Based on these results, it is demonstrated that this biosorbent represents a low-cost solution for the treatment of metal-polluted wastewaters.

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

Characterization of saline aqueous solutions upwelling under Ceres' surface: a focus on chemical equilibria in the H2O-CO2-NaCl supply ascent system

2019 ◽  
Author(s):  
Maria PEDONE ◽  
Eleonora Ammannito ◽  
Christina Plainaki ◽  
Maria Cristina De Sanctis ◽  
Andrea Raponi ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Chemical Equilibria

scholarly journals Study on Adsorption of Cu and Ba from Aqueous Solutions Using Nanoparticles of Origanum (OR) and Lavandula (LV)

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Ghadah M. Al-Senani ◽  
Foziah F. Al-Fawzan
Keyword(s):  
Heavy Metals ◽  
Particle Size ◽  
Free Energy ◽  
Aqueous Solutions ◽  
Thermodynamic Parameters ◽  
Solution Ph ◽  
Environment Friendly ◽  
Removal Of Heavy Metals ◽  
Equilibrium Data ◽  
Langmuir And Freundlich Models

Wild herbs (Origanum (OR) and Lavandula (LV)) were used as environment-friendly adsorbents in this study. The adsorbents were used for adsorption of Cu and Ba from water. The adsorption of heavy metals onto OR and LV was dependent on particle size, dose, and solution pH. The diameter of adsorbent particles was less than 282.8 nm. The adsorption follows second-order kinetics. Langmuir and Freundlich models have been applied to describe the equilibrium data, and the thermodynamic parameters, the Gibbs free energy, ∆G°, enthalpy, ∆H°, and entropy, ∆S°, have been determined. The positive value of ∆H° suggests that the adsorption of heavy metals by the wild herbs is endothermic. The negative values of ∆G° at all the studied temperatures indicate that the adsorption is a spontaneous process. It can be concluded that OR and LV are promising adsorbents for the removal of heavy metals from aqueous solutions over a range of concentrations.

scholarly journals Utilization to Remove Pb (II) Ions from Aqueous Environments Using Waste Fish Bones by Ion Exchange

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Bayram Kizilkaya ◽  
A. Adem Tekınay
Keyword(s):  
Aqueous Solutions ◽  
Adsorption Mechanism ◽  
Cost Effective ◽  
Isotherm Models ◽  
Maximum Adsorption Capacity ◽  
Fish Bones ◽  
Adsorption Capacities ◽  
Aqueous Environments ◽  
Equilibrium Data ◽  
Pseudo Second Order

Removal of lead (II) from aqueous solutions was studied by using pretreated fish bones as natural, cost-effective, waste sorbents. The effect of pH, contact time, temperature, and metal concentration on the adsorption capacities of the adsorbent was investigated. The maximum adsorption capacity for Pb (II) was found to be 323 mg/g at optimum conditions. The experiments showed that when pH increased, an increase in the adsorbed amount of metal of the fish bones was observed. The kinetic results of adsorption obeyed a pseudo second-order model. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of Pb (II) adsorption and the value ofRLfor Pb (II) was found to be 0.906. The thermodynamic parameters related to the adsorption process such asEa,ΔG°,ΔH°, andΔS° were calculated andEa,ΔH°, andΔS° were found to be 7.06, 46.01 kJ mol−1, and 0.141 kJ mol−1K−1for Pb (III), respectively.ΔH° values (46.01 kJmol−1) showed that the adsorption mechanism was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to the experimental equilibrium data. The fish bones were effectively used as sorbent for the removal of Pb (II) ions from aqueous solutions.

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