High School Students’ Conceptions about Energy in Chemical Reactions (focusing only in exothermic and endothermic reactions). Aim The aim of this study is to investigate students’ understanding of the energy concept in chemical reactions particularly in endothermic-exothermic reactions. Both qualitative and quantitative methodology was used for this investigation. A twenty-item multiple choice test was developed about the topic to measure the students’ understandings. This concept test was
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Chapter 1 Chemical Reactions and Equations Q.1. Why should magnesium ribbon be cleaned before burning in air ? Ans: Magnesium ribbon is a very reactive metal. When stored it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide being a stable compound prevents further reaction of magnesium with oxygen. The magnesium is cleaned before burning in air to remove this layer so that the metal can be exposed to air properly. Q.2. Write the balanced
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1. Determine the order of the reaction A --> 2B + C from the following data obtained for [A] as a function of time. time | [A] | 0 min | 0.80 M | 8 mins | 0.60 M | 24 mins | 0.35 M | 40 mins | 0.20 M | ------------------------------------------------- Use diferential and half life. 2. Balance the equation below and determine the rate expression using the given data. Find k with units. N2 + H2 ---> NH3 (all gaseous) [N2] (mole/L) | [H2] (mole/L) | Initial Rate (mole/L /min)
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Aldol In this preparative lab‚ an aldol (trans-p-anisalacetophenone) was produced from the reaction between p-anisaldehyde and acetophenone with the presence sodium hydroxide. The reaction also showed the importance of an enolate and the role it played in the mechanism. Sodium hydroxide acts as a catalyst in this experiment and is chosen because of its basic conditions and pH. The acetophenone carries an alpha hydrogen that has a pKa between 18 and 20. This alpha hydrogen is acidic because of its
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Chemical Reactions What is a Chemical Reaction? Types of Chemical Reactions Redox Reactions Nonredox Reactions Classifying Reactions What is a Chemical Reaction? A chemical reaction is a process in which the identity of at least one substance changes. A chemical equation represents the total chemical change that occurs in a chemical reaction using symbols and chemical formulas for the substances involved. Reactants are the substances that are changed and products are the substances that are
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Chemical Reactions Chemical reactions happen in almost everything around us. Reactions are very important in everyday life‚ and science. Chemical reactions are the changing of substances to other substances by the breaking of bonds in reactants and the formation of new bonds in products. There are different types of chemical reactions such as combination reaction‚ decomposition reaction‚ single-replacement reaction‚ double-replacement reaction‚ and combustion reaction. Combination
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endothermic reaction happened everywhere around us. Basically exothermic and endothermic reaction is transfer energy to the surroundings and take in energy from the surroundings (BBC GCSE bitesize). If the reaction forward ，then is exothermic.If the reaction is the backwards ‚then is endothermic. When a reaction take place‚ the energy started to transfer from different object to the surroundings or take away energy from the surroundings. When temperature started to change. Exothermic Reaction An exothermic
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The hypothesis If a chemical reaction occurs‚ then there will be indicators of a chemical change‚ was supported throughout this experiment. Throughout this experiment there were several reactions that took place‚ and an indicator of such chemical reactions could be seen throughout each one. The first piece of identifiable evidence was present in the first step‚ which was when copper (II) nitrate and sodium hydroxide were combined. When stirred‚ a blue precipitate formed at the bottom of the test
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determine the reaction time of the test participant and using the subtractive method identify the selection time and identification time of the participant. The experiments had one participant who participated in a total of 6 experiments; two experiments required a simple reaction with a single stimulus and 4 experiments that required a more complicated reaction. Keywords Subtractive method – the procedure of estimating the time it takes to perform various cognitive operations. Simple reaction – this
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SN1 Reactions For SN1 reactions it’s important to have a good leaving group because this reaction occurs in two steps. Because alcohol is such a poor leaving group it needs to be helped by silver nitrate to help promote the ionization of the alkyl halide. This helps form the products of the SN1 reaction. 2-chlorobutane This reaction didn’t occur because the carbocation isn’t stable enough for an SN1 reaction. 2-bromobutane This reaction occurred in 32 seconds. This reaction occurred quickly
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