Question

Red Cabbage Lab

1.

Besides boiling Red Cabbage in water, another way to extract the anthocyanins is to

	A.	freeze the red cabbage on dry ice
	B.	heat the red cabbage in a drying oven at 200 C
	C.	place the red cabbage in an alcohol solution
	D.	shake the red cabbage in a bag with sodium bicarbonate

2.

Which of the following may also be used to extract anthocyanins to use as pH indicators?

	A.	apples
	B.	blueberries
	C.	black raspberries
	D.	strawberries
	E.	all of the above

3.

QUESTION 4

Which of the following best explains how a pH indicator works?

	A.	a pH indicator is one color at one pH and a different color at a higher pH and it is usually just a difference of one proton (H+) in the structures between the two colors
	B.	a pH indicator is one color at one pH and a different color at a higher pH and it is usually just a difference of one electron in the structures between the two colors
	C.	a pH indicator is one color at one pH and a different color at a higher pH and it is usually just a difference of one carbon in the structures between the two colors
	D.	a pH indicator is one color at one pH and a different color at a higher pH and it is usually just a difference of one carbonyl in the structures between the two colors

4.

What is unique about red cabbage extract pH indicator compared to pH paper?

	A.	red cabbage extract is made up of small molecules while pH paper uses large molecules
	B.	red cabbage extract is mostly one molecule that changes at least three different colors at different pH ranges while pH paper is typically made up of several different molecules changing different colors at different pH ranges
	C.	red cabbage extract molecules chemically change their molecular structure in a major way when they change color in different pH ranges while compounds in pH paper typically change by just a proton when they change colors in different pH ranges
	D.	red cabbage extract has a long shelf life when stored at room temperature while pH paper can only be stored at room temperature for several months before it expires

5.

Copy below and enter the information and data/observations as listed for each liquid tested in the experiment:

Liquid Tested:__________________

Red Cabbage Extract Color ___________ and interpreted pH [   ]

pH Paper Color __________ and interpreted pH [   ]

Answer 1

1) Correct option is C. place the red cabbage in an alcohol solution

Explanation- the mixture of 50% (v/v) ethanol and acidified water is used to extract anthocyanin from red cabbage.                             

2) Correct option B. blueberries

Explanation -Blueberries has dark blue, because it contains anthocyanins. Anthocyanins are pH sensitive and used as pH indicators. They are red in acidic solutions and blue in basic.

3) Correct option A. a pH indicator is one color at one pH and a different color at a higher pH and it is usually just a difference of one proton (H+) in the structures between the two colors

Explanation - Acids donate protons (H⁺) and bases accept protons (H⁺).A pH indicator is one color in acidic solution a different color in basic solution.

4) Correct option B. red cabbage extract is mostly one molecule that changes at least three different colors at different pH ranges while pH paper is typically made up of several different molecules changing different colors at different pH ranges

Red cabbage contains an anthocyanin dye that can be used as a pH indicator. It is red or magenta in acids, (pH < 7), purple in neutral solutions and ranges from blue to green to yellow in alkaline solutions (pH > 7).