Understanding pH Indicators

The video tutorial explains how to measure the pH of a solution both quantitatively and qualitatively. It introduces various indicators, such as Universal Indicator, litmus paper, phenolphthalein, and methyl orange, which change color at different pH levels. Universal Indicator can measure the full pH scale, while litmus paper is used for basic acidic and alkaline tests. Phenolphthalein and methyl orange are used in titrations to determine end points. The video concludes by summarizing the importance of indicators in determining pH levels.

What is the primary function of an indicator in pH measurement?

• To measure temperature

• To change the solution's pH

• To measure the solution's volume

• To indicate the pH by changing color

Which of the following is true about the Universal Indicator?

• It measures pH from 0 to 7 only

• It can measure pH across the entire scale from 0 to 14

• It only works in acidic solutions

• It is a single chemical compound

What color does the Universal Indicator turn in a strongly acidic solution?

• Green

• Deep red

• Dark blue

• Yellow

What does a green color in a Universal Indicator signify?

• Weakly acidic

• Strongly alkaline

• Neutral

• Strongly acidic

How does blue litmus paper react in acidic conditions?

• It remains unchanged

• It turns red

• It turns green

• It turns blue

What is the color change of phenolphthalein at a pH of 8.2?

• Yellow to green

• Blue to red

• Colorless to fuchsia pink

• Red to yellow

At what pH does methyl orange change from red to yellow?

• Above 4.4

• Below 3.1

• At 8.2

• At 7

Which indicator is commonly used in strong acid-strong alkali titrations?

• Litmus

• Phenolphthalein

• Universal Indicator

• Bromothymol blue

What is the endpoint of an indicator?

• The point where the solution freezes

• The point where the indicator changes color

• The point where the solution boils

• The point where the solution evaporates

Which of the following is NOT a common pH indicator?

• Sodium chloride

• Phenolphthalein

• Litmus

• Universal Indicator