• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.247-255
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• 2006

The purpose of this study was to investigate the correlation between concepts on chemical reaction rates and concepts on chemical equilibrium in high school students. The subjects of the investigation consisted of 120 third grade students attending high school in K city of Kyunggi province. For this study, questionnaire relevant to the subject of chemical reaction rates and chemical equilibrium was developed and the answers were analyzed. As a result of the study, a large percentage of high school students answered questions on reaction rates correctly, but only a small percentage of the students could give explanations. Many high school students answered questions on the rates of forward reactions correctly, but not the questions on the rates of reverse reactions. For the concepts on chemical equilibrium, many high school students gave correct answers when faced with equilibrium questions that only required the understanding of one side of the reaction. But the students could not answer the questions requiring understanding of both forward and reverse reactions as well. Overall, there was a little high correlation between concepts on chemical reaction rates and concepts on chemical equilibrium in high school students. Especially, high school students with little understanding of reverse reaction rates did not understand that chemical equilibrium is a dynamic equilibrium. Also, high school students with little understanding of the collision mechanism regarding chemical reaction rates did not understand the effect of concentration and catalyst factors on chemical equilibrium. And the correlation between concepts on chemical reaction rates and concepts on chemical equilibrium related to concentration and catalyst factors was low. In conclusion, the formation of scientific concepts on chemical reactions rates can decrease misconceptions on chemical equilibrium. Also the teaching-learning method limited to one side of a reaction can cause difficulty in forming the concepts on chemical dynamic equilibrium. Therefore, the development of a teaching-learning method which covers both the forward and reverse reactions can be effective in helping students form the concepts on chemical equilibrium.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.365-374
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• 2007

The purpose of this study is to investigate the students' conceptions about the reaction rate changes during the chemical equilibrium shifts and also whether the questions about basic concepts of the reaction rate are helpful for the students' understanding of reaction rate changes during the chemical equilibrium shifts. The subjects were 100 students in the 12th grade. The questionnaires were composed of A, B, and A' set, which had to be answered sequentially. The A set consisted of questions asking the change of reaction rate when chemical equilibrium was shifted, the B set was to testify the basic concepts of the reaction rate, and the A' set was the same as the A set. The results showed that the students' understanding of the reverse reaction rate change was lower than that of the forward reaction rate change during the equilibrium shift. Also it was found that students' understanding of the reaction rate change caused by adding the reactant was fairly good while their understanding of the reaction rate change caused by temperature increment was very poor. Since the students marked very high scores in the B set questions, their poor understanding for the reaction rate changes during the equilibrium shifts was not seemed to be due to the lacks of the basic knowledge of reaction rate. Instead, it was due to the failure of applying the basic knowledge of reaction rate to the changes of reaction conditions. It was also found that the average scores of A' set were statistically higher than those of A set. It means the B set items were helpful for the students to solve the A' set items. These results evidenced the possibility of set questionnaires could help the students to connect the related concepts in solving the problems.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.265-278
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• 2002

A concept test was administered to college students and teachers to identify their understanding of chemical equilibrium and equilibrium shift. The subjects were 53 freshmen in the General Chemistry class, 28 juniors in the Physical Chemistry class and 26 seniors from a university and 10 high school teachers in Seoul. Test items include the calculations of partial pressure and concentration of the gas in the mixture, the equilibrium constant cal-culation and the prediction of equilibrium shift when an inert gas is added to the gaseous reaction system, and the equilibrium concentration calculation and the prediction of equilibrium shift when water or common ion is added to the weak acid solution. The test was focused to identify whether the subjects can predict equilibrium shift using the reaction quotient change for the situations in which Le Chatelier principle is difficult to apply. The results showed that the achievements of teachers and juniors were significantly higher than those of freshmen and seniors. Many stu-dents had difficulties in predicting equilibrium shift using the reaction quotient while they could calculate partial pres-sure and concentration for the same situation. It means they are lack of conceptual understanding of chemical equilibrium shift.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.333-342
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• 2016

Liquid rocket propulsion is a system that produces required thrust for satellites and space launch vehicles by using chemical reactions of a liquid fuel and a liquid oxidizer. Monomethylhydrazine/dinitrogen tetroxide, liquid hydrogen/liquid oxygen and RP-1/liquid oxygen are typical combinations of liquid propellants commonly used for the liquid rocket propulsion system. The objective of the present study is to investigate useful design and performance data of liquid rocket engine by conducting a numerical analysis of thermochemical reactions of liquid rocket propellants. For this, final products and chemical compositions of three liquid propellant combinations are calculated using equilibrium constants of major elementary equilibrium reactions when reactants remain in chemical equilibrium state after combustion process. In addition, flame temperature and specific impulse are estimated.

• Proceedings of the Membrane Society of Korea Conference
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• 1992.10a
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• pp.43-44
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• 1992

촉매막반응기란 반응기와 분리막이 동시에 하나의 과정으로 결합된 unit로, 촉매막반응기를 사용할 경우 가역 반응에서 막을 통한 생성물의 선택적 제거는 화학 평형이동을 유발시켜 열역학적으로 얻을수 있는 평형 전환율보다 높은 전환유을 얻을 수 있다. 본 연구는 이러한 촉매막반응기의 성능에 대한 실험적 연구로, 산 촉매하에서 일어나는 MTBE 분해반응을 12-텅스토인산 촉매상에서 수행하였다.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.731-738
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• 2012

The purpose of this study is to analyze the understandings of science high school students on the conception of chemical cell in relation to chemical equilibrium from the microscopic viewpoint at molecular level through questionnaires and follow-up interviews. The results show that they have high understandings on the chemical equilibrium states in the electrochemical cell and on the redox reaction taking place simultaneously when a metal electrode is immersed in the metal ion solution. However, they do not fully comprehend the development of electrical potential difference, electron movement, electrode potential measurement in the half-cells, and calculation of the net cell voltage between anode and cathode in the chemical cell because of difficulties in the microscopic understanding the interaction on the interface at the electrode and the electrolyte solution.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.83-84
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• 2001

액적화학은 SO4$^{-2}$ 생성에 중요한 역할을 할 뿐만 아니라 OH와 HO$_2$ 라디칼 생성에도 영향을 미친다. 따라서 기존 기상 광화학반응에 액적화학을 추가하여 산성비 모사를 하여왔다. 그러나 액적화학을 추가하기 위해서는 기액간의 물질전달을 포함하여야 하고 액적화학반응속도와 기상화학반응속도가 크게 다름으로써 수치적 풀이의 어려움이 가중되는 문제가 있다. 따라서 기존 연구에서는 기액간의 평형 및 시간 분리 등의 가정을 사용하여 액적화학 반응 추가에 따른 문제를 해결하여 왔다. 본 논문은 이러한 수치단순화의 정확도를 평가하려 한다. (중략)

• Polymer(Korea)
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• v.29 no.3
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• pp.304-307
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• 2005

The acid-catalyzed hydrolysis reaction of poly(vinyl acetate) (PVAc) in water/acetic acid solution at $35^{circ}C$ was studied at two different solvent compositions. The mole fractions of vinyl acetate (Vac) and vinyl alcohol (VA) during the course of the reaction were determined by NMR, and the equilibrium constant $K_{eq}$ of the reaction was determined using the molar ratio of VAc to VA at the chemical equilibrium. $K_{eq}$ was 0.75 (${\pm}0.01$) when the VAc mole faction at the equilibrium was 0.78 (${\pm}0.01$) and it was 0.69 (${\pm}0.01$) when the VAc mole fraction was 0.57 (${\pm}$0.02). The reaction was found to be a pseudo 1-st order reaction with the rate coefficient at $3.4{\times}10^{-6}/sec$.

• Journal of Energy Engineering
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• v.2 no.3
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• pp.276-284
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• 1993

This study is to obtain some basic data which are prerequisite for the conceptual design of gasification process based on entrained-bed type gasifier. The Gibbs free energy minimization method is used to analyze the chemical equilibrium in the gasifier. The modeling results which consider the conventional mass balance and heat balance are compared with the experimental data published by Electric Power Research Institute. The analysis shows that the reaction in a entrained-bed gasifier is influenced mainly by the amount of oxidant, by the temperature of gasifier and by the type of coals.

• 한국과학교육학회:학술대회논문집
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• 2008.08a
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• pp.102.1-102.1
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• 2008