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自然科學 大學

為什麼[A(org)]=n[An(org)]成立 (第三張圖equation 7.9) 感謝

Experiment 7 Experiment 7 The partition of Organic acid between Water and Organic solvent Objectives Understand the partition of a solute between two immiscible solvents. Introduction A chemical analysis that is performed primarily with the aid of volumetric glassware (e.g., pipets, burets, volumetric flasks) is called a volumetric analysis. For a volumetric analysis procedure, a known quantity or a carefully measured amount of one substance reacts with a to-be-determined amount of another substance with the reaction occurring in aqueous solution. The volumes of all solutions are carefully measured with volumetric glassware. The known amount of the substance for an analysis is generally measured and available in two ways: 1. As a primary standard: An accurate mass (and thus, moles) of a solid substance is measured on a balance, dissolved in water, and then reacted with the substance being analyzed. 2. As a standard solution: A measured number of moles of substance is present in a measured volume of solution - a solution of known concentration, generally expressed as the molar concentration (or molarity) of the substance. A measured volume of the standard solution then reacts with the substance being analyzed. The reaction of the known substance with the substance to be analyzed, occurring in aqueous solution, is generally conducted by a titration procedure. The titration procedure required a buret to dispense a liquid, called the titrant, into a flask containing the analyte. A reaction is complete when stoichiometric amounts of the reacting substances are combined. In a titration this is the stoichiometric point. In this experiment the stoichiometric point for the acid-base titration is detected using a phenolphthalein indicator. Phenolphthalein is colorless in an acidic solution but pink in a basic solution. The point in the titration at which the phenolphthalein changes color is called the endpoint of the indicator. Indicators are selected so that the stoichiometric point in the titration coincides (at approximately the same pH) with the endpoint of the indicator.

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英文 高中

英文問題 may not be什麼意思 感覺題目詳解給錯了

第 48 至 51 題為題組 Many of us have probably experienced déjà vu at least a few times in our life. Its meaning comes from the phrase "already seen" in French, and occurs when we feel that a person, place, or thing is familiar to us without actually having experienced them before. This strange phenomenon happens to as much as 70 percent of the population, but a higher number of 15 to 25 year olds experience it than any other age group. Maybe you just travelled to a new foreign country, and it just felt very familiar to you. Yes, you are feeling déjà vu; however, you know you haven't been there before. While different people experience déjà vu in different ways, it is still a pretty mysterious phenomenon, and researchers are putting the pieces together. Based on some studies, déjà vu is just a part of having a healthy memory checking system, and people who experience déjà vu more often are less likely to forget the details of important events. In fact, the results of the study don't look too promising in terms of mental health for people who never experience déjà vu. Scientists believe déjà vu is created by a neurological anomaly related to an improper electrical discharge in the brain. In short, it's not a mystical prophecy or out-of-body experience, but just your brain playing a trick on you; that is, these scientists dismiss it as just a glitch in the matrix. A few people are just terrified when it happens, but others feel euphoric about it. On average, most people just find it to be a perplexing sensation, neither pleasant nor threatening. Since déjà vu occurs in individuals with and without a medical condition, there is much speculation as to how and why it happens. Several psychoanalysts attribute deja vu to simple fantasy or wish fulfillment, while some psychiatrists ascribe it to a mismatching in the brain that causes it to mistake the present for the past. Many parapsychologists believe it is related to a past-life experience. Obviously, there is more investigation and researches to be done. So, does this article seem very familiar to you? 48. Which of the following CAN'T be described as a déjà vu experience based on this passage? (A) You keep buying similar style of clothing and you don't know why. (B) You feel you've been to a place when actually it's your first time there. (C) Someone looks familiar to you though you have never seen him before. (D) You just met a new friend whom you think you must have met somewhere. 49. Based on the article, which description about déjà vu is WRONG? (A) It actually is not as harmful to our mental health as we think. (B) Some people who have experienced it may feel a sense of happiness. (C) The word"déjà vu" originates from France, meaning"already seen." (D) Those who never experience it may not be mentally healthier than those who do.

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