• Journal of the Korean Chemical Society
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• v.52 no.3
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• pp.303-314
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• 2008

The purpose of this study was to understand the experiment for measuring chemical reaction rate by precipitate formation and to develop experiments applying small-scale chemistry. For this study, the experimental method for measuring the effect of concentration and temperature on chemical reaction rates presented in the 10 high school science textbooks were classified by their experimental methods of confirming production. Subsequently, problems observed in carrying out the experiments for measuring chemical reaction rates by precipitate formation frequently presented in the 10 high school science textbooks were analyzed. Experiments applying small-scale chemistry were developed measuring chemical reaction rate by precipitate formation. According to the result of this study, there were some problems in the experimental method of precipitate formation for measuring chemical reaction rates presented in the high school science textbooks. Those problems in the science textbook experiments were insufficient specification of mixing methods of reaction solutions, obscurity of knowing when the character letter X disappeared, time delay in collecting the experimental data, formation of hazardous sulfur dioxide, uneasiness of fixing water bath container, controlling the reaction temperature, and low reproducibility. Those problems were solved by developing experiments applying smallscale chemistry. Presenting the procedure of mixing reaction solutions on the A4 reaction paper sheet made the experimental procedure clearly, using well plates and stem pipette shortened the reaction time and made it possible to continuously collect the experimental data. Furthermore, the quantity of hazardous sulfur dioxide was reduced 1/7 times and the time when the character letter X disappeared could be observed clearly. Since experiments for measuring the effect of concentration and temperature on chemical reaction rates could be performed in 30 minutes, the developing experiments applying SSC would help students understand the scientific concepts on the effect of concentration and temperature on chemical reaction rates with enough time for experimental data analysis and discussion.

• Resources Recycling
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• v.12 no.4
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• pp.30-37
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• 2003

A kinetics study on the dissolution reaction of zinc-ferrite has been made with aqueous sulfuric acid in various temperature and concentration. Fraction reacted(R) and apparent rate constant(K) increased with increasing temperature and concentration of sulfuric acid solution. The rate of dissolution is shown by $1-(1-K)^{1/3}=Kt$ for the initial stage of the reaction in aqueous sulfuric acid, where K is apparent rate constant, R is fraction reacted and t is reaction time, respectively. Activation energy associated with reaction was determined to be 16.3 kcal/mole. The dissolution of zinc-ferrite in sulfuric acid solution is dissolved by sto-ichiometric composition, but Fe and Zn did not dissolved, respectively.

• Journal of the Korean Society of Clothing and Textiles
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• v.16 no.2
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• pp.181-187
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• 1992

일반적으로 면섬유는 햇빛에 의해서 변색되거나 약해지며 또 그 외에도 여러가지 물리적, 화학적인 변화를 일으키게 된다. 구체적인 화학반응의 메카니즘은 사용되는 광선의 스펙트럼, 대기조건(실내인 경우는 실내 환경조건) , 산소의 유무 그리고 염료 등 첨가물의 종류와 같은 여러 요소에 의해 크게 영향을 받게 된다. 환경조건 중에서 산소의 존재는 매우 중요하지만 open system에서 산소의 농도가 일정하다고 가정할 때 면섬유가 접하고 있는 환경조건 중에서 온도와 습도는 photodegradation의 속도를 결정짓는 중요한 요인으로 작용하게 된다. 박물관,:기념관, 도서관 등의 소장품이 자연광선이나 인공조명으로부터 손상되는 것을 막기 위해서는 먼저 이들의 photodegradation 현상에 대한 연구를 필요로 한다. 본 연구에서는 면시칩포를 자연광선과 가장 흡사한 스펙트럼을 가진 xenon arc lamp를 사용한 내후도 시험기내에서 온도와 습도를 조절하여 이에 따른 반응속도의 차이를 인열강도의 감소와 중합도 저하로 측정하였다. 1차 반응식은 실험결과를 설명하는데 유용하였으며 온 · 습도의 증가는 반응속도를 증가시키는 것으로 나타나 기존의 상반된 연구결과의 차이를 입증하였다. 또 온도와 습도는 상호관련이 있는 것으로 나타났으며 고온인 경우습도의 영향을 더 크게 받는 것으로 분석되었다. 반응의 활성에너지는 $30\~75\%$ RH에서는 12 kcal/mole 정도이며 수분의 함량이 낮을수록 활성화에너지는 커지는 것으로 나타나 수분은 섬유소 분자구조내에서 가소제 (plasticizer)의 역할을 하는 것으로 판명되었다.

• Journal of the Korean Chemical Society
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• v.38 no.4
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• pp.265-270
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• 1994

The aquation and base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ were studied by UV spectroscopic method in various SDS aqueous solution. The base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ with the addition of 0, 0.05, 0.1 mol dm$^{-3}$ sodium chloride was studied. For the aquation of the complex, the rate constant in the micellar phase(kH$^M$) was a little larger than that in the aqueous phase(kH$^W$). With the increase of SDS concentration, the second order rate constant(kOH) for the base hydrolysis unchanged below the CMC and sharply decreased down to a limiting value after the CMC was reached. The effect of added NaCl on the rate behavior of the complexes in the micellar solution were investigated by using an ion-exchanged model.

• Resources Recycling
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• v.24 no.6
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• pp.24-30
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• 2015

The sulfuric acid leaching of ferromanganese dust was studied. The effect of acid concentration, reaction temperature, stirring rate, particle size and solid to liquid ratio on Mn and Fe extraction in the solution were investigated. It was found that the leaching rate of Mn and Fe increased with increasing reaction temperature and sulfuric acid concentration. Examination of data by shrinking core model suggested that the leaching rate is controlled by chemical reaction at the surface of particle. The activation energy for the leaching reaction of Mn and Fe were calculated to be 79.55 kJ/mol and 77.48 kJ/mol, respectively.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.292-302
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• 2009

The wet oxidation of phenol has been investigated at temperatures from 150 to $250^{\circ}C$ and oxygen partial pressures from 25.8 to 75.0 bar with initial pH of 1.0 to 12.0 and initial phenol concentration of 10 g/l. Chemical Oxygen Demand COD has bee measured to estimate the oxidation rate. Reaction intermediates have been identified and their concentration profiles have been determined using liquid chromatography. The destruction rate of phenol have shown the first-order kinetics with respect to phenol and the changes in COD during wet oxidation have been described well with the lumped model. The impact of various homogeneous catalysts, such as $Cu^{2+}$, $Fe^{2+}$, $Zn^{2+}$, $Co^{2+}$ and $Ce^{3+}$ ions, on the destruction rate of phenol and COD has also been studied. The homogeneous catalyst of $CuSO_4$ has been found to be the most effective for the destruction of phenol and COD during wet oxidations. The destruction rate of formic acid formed during wet oxidations of phenol have increased as increasing temperature and $CuSO_4$ concentration. The final concentrations of acetic acid which has been formed during wet oxidations and difficult to oxidize have increased with reaction temperature and with decrease in the catalyst load.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.1062-1067
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• 1994

The chemistry of 5-methyl-4-imidazolecarboxylic acid ester synthesis involves three distinct reaction steps. Of these the rate of formation of diketone was found to be a function of oxime and HCl concentration and temperature by the batch experiment. The decomposition of diketone was found to be a slow process whereas temperature was the only variable to affect it significantly. An empirical rate expression for the net formation of diketone fits the experminetal data satisfactorily. The principal objectives of this study are to study the kinetics of the diketone formation reaction and to develop the empirical rate expression.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.294-295
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• 1997

CO-Cr 수직자기기록 매체의 우수한 하지층을 개발하기 위하여, 스피넬 결점막$(Fe,M)_3O_4$ (M=Ni,Zn)이 스핀스프레이 페라이트 플레이팅 방법으로 유리 기판 위에 제작되었다. 반응액과 산화액은 기판이 회전하는 반응용기로 분사되었다. 반응은 기판의 회전소독, 반응온도, 반응액과 산화액의 유속 그리고 반응액과 산화액의 농도에 의해 영향받았다. 반응액과 산화액의 유속은 60(ml/min)으로 하고, 반응온도는 90[$^{\circ}C$] 그리고 기판의 회전속도는 150[rpm]의 조건하에서, 페라이트 플레이팅 반응에 미치는 반응액과 산화액 농도의 영향이 화학적 조성, 결정학적 및 자기적 특성의 관점에서 연구되었다. $Ni_{0.34}Zn_{0.66}Fe_2O_4$의 조성에서, 우리는 가장 안정한 결정학적 및 자기적 특성을 얻었다.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.166-171
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• 2001

In an aluminum-air unit cell used alkaline solution, Hydrogen evolution rates were investigated far the observation of the effects of alloy element, inhibitor and its concentration in electrolyte, KOH concentration, solution temperature, and current density loaded to cell. Hydrogen evolution rates were reduced up to $50\%$ by saturating the solution with ZnO, while ZnAc(Zinc Acetate) did not work as inhibitor. The inhibition effect of ZnO increased with increasing the KOH concentration and solution temperature. They were linearly increased with the KOH concentration and current density in first order and exponentially increased with the solution temperature.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.308-314
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• 1997

The effects of catalyst and blocking reagents(BR) on the blocking reactions of TDI and MDI in the preparation of polyurethane varnishes have been studied. It was found that certain types of catalysts, such as 1,4-diazabicyclo[2.2.2]octane(DABCO) and tetramethyl guanidine(TMG), were necessary to complete the NCO blocking reactions. Blocking rate of TMG was shown much faster than that of DABCO. Reactivity increased with the increase of TMG concentration, at least to the concentration of 1%. In case of DABCO, the 0.25% concentration of catalyst showed the highest reactivity. In order to study the steric effects of BR on the blocking reactions, phenol, p-cresol, m-cresol, o-cresol, 2,4-xylenol were used as blocking reagents. As expected, BR which has less steric hindrance showed higher reactivity. The increase in BR concentration and reaction temperature increased the productivity of polyurethanes in this reaction system.