"Testing the Acidity and Alkalinity of Solutions" Acids and Alkalis PPT Courseware 2

"Testing the Acidity and Alkalinity of Solutions" Acids and Alkalis PPT Courseware 2

Purpose

1. Preliminarily learn to use acid-base indicators to test the acidity and alkalinity of solutions.

2. Preliminarily learn to use pH test paper to measure the acidity and alkalinity of a solution.

Experimental supplies

1. Instruments: beaker, test tube, mortar, glass rod, gauze.

2. Drugs: distilled water, alcohol, phenolphthalein solution, litmus solution, pH test paper, plant petals or fruits, soil samples, vinegar, sucrose solution, plant ash water, soapy water, lime water.

Activity experience

1. Test the acidity and alkalinity of the solution:

【Experimental steps】

(1) Homemade acid-base indicator: Take the petals or fruits of morning glory, marigold, carrot, and rose and mash them in a mortar, add alcohol to soak them, and filter or squeeze out the soaked juice with gauze. And mark them separately.

(2) Choose vinegar, sucrose solution, plant ash water, soapy water, and lime water in daily life, and conduct the following experiments:

① Add phenolphthalein solution and litmus solution dropwise to the test tubes containing the above solutions, and observe the color changes.

② Use pH test paper to measure the pH of five solutions: vinegar, sucrose solution, plant ash water, soapy water, and lime water.

③Test the color changes of the self-made indicator in five solutions: vinegar, sucrose solution, plant ash water, soapy water, and lime water.

[Experimental phenomena and records]

(1) Phenolphthalein is added dropwise to vinegar and sucrose solution _______, and added dropwise to plant ash water, soapy water, and lime water _______.

(2) Litmus is added dropwise to vinegar solution_______, added dropwise to sucrose solution_______, and added dropwise to plant ash water, soapy water, and lime water_______.

(3) The pH of vinegar is ___, the pH of sucrose solution is __, the pH of plant ash water is ___, the pH of soap water is ___, and the pH of lime water is ___.

【Experimental results】

(1) The vinegar solution has a _____, pH___, which can make the litmus solution become _____ and the phenolphthalein solution _______.

(2) The sucrose solution is _____, pH___, and cannot change the color of litmus solution and phenolphthalein solution.

(3) The solutions of plant ash water, soapy water and lime water are _____ and pH___, which can make the litmus solution turn into _____ and the phenolphthalein solution turn into _____.

(4) The juices of _______ and _____ can be used as acid-base indicators, but the juices of _______ and ________ cannot be used as acid-base indicators.

Experimental drill

1. (2012·Suzhou High School Entrance Examination) Which of the following operations to detect the pH of a solution is correct ()

A. Put the pH test paper into the liquid to be tested and compare it with the standard color card reading.

B. Use a dry, clean glass rod to dip a small amount of the liquid to be tested, and put it on the pH test paper placed on a clean watch glass. Within half a minute, according to the color of the test paper, compare the reading on the standard color card.

C. Use a glass rod to dip the liquid to be tested onto the pH test paper moistened with distilled water, and compare it with the standard color card reading.

D. Dip the glass rod into the liquid to be tested and put it on the pH test paper. After 3 minutes, compare the reading with the standard color card.

[Analysis] Choose B. The correct operation for measuring the pH of a solution is to use a dry, clean glass rod to dip a small amount of the liquid to be tested, and put it on the pH test paper placed on a clean watch glass. Within half a minute, according to the color of the test paper, compare it with the standard color card reading. So choose B.

2. (2012 Tianjin High School Entrance Examination) A student used pH test paper to measure the pH of some liquids in daily life. His experimental records must be wrong ()

A. Soap water pH=10 B. Soda ash solution pH=11

C.Orange juice pH=4 D.Vinegar pH=7

[Analysis] Choose D. This question tests students' ability to judge the acidity and alkalinity of a solution. The key to answering this question should be clear about two points: (1) Both soapy water and soda ash solutions are alkaline, with pH>7. (2) Orange juice and vinegar are both acidic, with pH<7.

3. Soak Phalaenopsis in alcohol and water to obtain a purple solution, which will appear red when exposed to acidic solutions and yellow when exposed to alkaline solutions. Which of the following statements is correct ()

A. The red color of the Phalaenopsis solution and acid is a physical change.

B. What can make the solution of Phalaenopsis turn yellow must be an alkali

C. After dropping the salt solution into the solution of Phalaenopsis, the solution is still purple.

D. Phalaenopsis solutions cannot be used as acid-base indicators

[Analysis] Choose C. The solution of Phalaenopsis that appears red when exposed to acid is a chemical reaction with the acid to form new substances, which is a chemical change; the solution that can make the solution of Phalaenopsis appear yellow is alkaline, but is not necessarily an alkali solution; salt solution It is neutral, so after dropping the solution of Phalaenopsis, the solution is still purple; the solution of Phalaenopsis can show different colors when exposed to acid and alkali, and can be used as an acid-base indicator.

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"Testing the Acidity and Alkalinity of Solutions" Acids and Alkalis PPT courseware:

"Testing the Acidity and Alkalinity of Solutions" Acids and Alkalis PPT Courseware Experimental Process Please conduct the experiment according to the experimental steps on P70 of the textbook, and summarize the differences between the acidity and alkalinity of solutions and the detection methods of solution acidity and alkalinity and pH. Acid-base: We can use the acid-base index...