【Daily Question】Nov. 3, 2015: Participation +2 Wealth； +3 to 8 wealth for correct answers
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This post was last edited by zjp on 2015-11-4 09:06. To increase the popularity of the chemical analysis section, a \"One Question per Day\" campaign has been launched; this aims to foster active technical exchanges while also providing financial rewards to users. 【Daily Question】 (Single-choice question) In the iodometric method, starch is the specific indicator; when the solution turns blue, this indicates ( ). A. The color of iodine B. The color of I- C. The color of the product formed by free iodine and starch D. The color of the product formed by I- and starch. Please post your answers in the replies; answering correctly earns you +2 wealth points. Getting all answers right grants an additional +3 to +8 wealth points. Those who provide a thorough analysis or explanation of the questions and answers, or include detailed calculation processes, will receive extra wealth points as a reward. If your answers are correct and your analysis and explanations are accurate, they will be marked as the best reply (or the best assistance). Feel free to answer the questions. Note: We will close this post after 24 hours, and at that time we will announce the best reply (the best assistance), as well as the answer and explanation.
In the iodometric method, starch is the specific indicator; when the solution turns blue, this indicates (C).
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C....................................
In the iodometry method, starch is the specific indicator; when the solution turns blue, this indicates (D). A The color of iodine B The color of I- C The color of the product formed by free iodine and starch D The color of the product formed by I- and starch
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In the iodometry method, starch is the specific indicator; when the solution is blue, this indicates ( ). A The color of iodine B The color of I- C The color of the product formed by free iodine and starch D The color of the product formed by I- and starch
In the iodometry method, starch is the specific indicator; when the solution turns blue, this indicates (c). A The color of iodine B The color of I- C The color of the product formed by free iodine and starch D The color of the product formed by I- and starch
In the iodometric method, starch is the specific indicator; when the solution turns blue, this indicates (C). A The color of iodine B The color of I- C The color of the product formed by free iodine and starch D The color of the product formed by I- and starch
At a pH of 2 to 9, the starch indicator is most sensitive in weak acidic media. When pH is greater than 9, I2 tends to undergo disproportionation reactions to form IO and IO3; these substances do not produce a color reaction with starch. When pH is less than 2, starch easily hydrolyzes into dextrin, and dextrin turns red in the presence of I2. This color reaction is poorly reversible. Amylose is usually used: Amylose must have iodide ions present in order to turn blue when exposed to iodine ； Amylopectin turns purple when exposed to iodine, and the color change is not sharp.
In the iodometry method, starch is the specific indicator; when the solution turns blue, this is the color of the complex formed between free iodine and starch.