pH指示剂彩虹

绘制整个pH范围内的指示剂变色图

Qualitative Analysis Beginner (Middle School) 45 分钟 ~$8.00

目标

观察不同pH指示剂在特定pH值下的颜色变化，理解指示剂变色范围的概念。

背景

pH indicators are weak acids or bases whose conjugate forms have different colors. Each indicator has a characteristic transition range where it changes color. By testing multiple indicators across a range of buffered solutions, students create a visual map of indicator behavior that reinforces concepts of acid-base equilibrium and the Henderson-Hasselbalch equation.

安全警告

  • Indicators can stain skin and clothing
  • Extreme pH solutions (pH 1, 14) are corrosive
  • Avoid mixing different buffer solutions

所需PPE

goggles lab_coat

材料

  • Buffer solutions (pH 1–14) (5 mL each)
    Pre-prepared set
  • Methyl orange indicator (5 mL)
    pH 3.1–4.4 range
  • Bromothymol blue indicator (5 mL)
    pH 6.0–7.6 range
  • Phenolphthalein indicator (5 mL)
    pH 8.2–10.0 range
  • Universal indicator (5 mL)
    Full pH range
  • Litmus solution (red and blue) (5 mL each)
    Simple acid/base test

设备

Spot plate or microwell plate Dropper pipettes (one per indicator) pH meter or pH paper White background paper

步骤

1

Arrange the spot plate and add 10 drops of each buffer solution (pH 1 through 14) across each row.

10 分钟 Handle pH 1 and 14 solutions carefully
2

Add 2 drops of methyl orange to the first row of buffer solutions. Record the color at each pH.

5 分钟
3

Add 2 drops of bromothymol blue to the second row. Record the color at each pH.

5 分钟
4

Add 2 drops of phenolphthalein to the third row. Record the color at each pH.

5 分钟
5

Add 2 drops of universal indicator to the fourth row. Observe the full rainbow of colors.

5 分钟
6

Create a color chart recording each indicator's color at every pH level. Identify each indicator's transition range.

15 分钟

预期结果

Methyl orange: red (acidic) to yellow (basic) around pH 3–4. Bromothymol blue: yellow to blue around pH 6–7.6. Phenolphthalein: colorless to pink around pH 8–10. Universal indicator: red through violet across the full pH range.

清理

Pour solutions into the appropriate waste container (acid or base). Rinse spot plates thoroughly with distilled water.

详情

类别
Qualitative Analysis
难度
Beginner (Middle School)
时长
45 分钟
预估费用
$8.00
步骤数
6
材料
6

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Frequently Asked Questions

What is the objective of pH指示剂彩虹?
观察不同pH指示剂在特定pH值下的颜色变化，理解指示剂变色范围的概念。
How difficult is pH指示剂彩虹?
This experiment is rated as Beginner (Middle School). It takes approximately 45 minutes to complete.
What safety precautions are needed for pH指示剂彩虹?
Key safety precautions include: Indicators can stain skin and clothing; Extreme pH solutions (pH 1, 14) are corrosive; Avoid mixing different buffer solutions.
What materials are needed for pH指示剂彩虹?
The main materials required are: Buffer solutions (pH 1–14), Methyl orange indicator, Bromothymol blue indicator, Phenolphthalein indicator, Universal indicator.
What results should I expect from pH指示剂彩虹?
Methyl orange: red (acidic) to yellow (basic) around pH 3–4. Bromothymol blue: yellow to blue around pH 6–7.6. Phenolphthalein: colorless to pink around pH 8–10. Universal indicator: red through violet across the full pH range.