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2 years ago

Determine whether each chemical substance would remain the same color or turn pink in the presence of phenolphthalein.

Chemistry

1 answer:

Serhud [2]2 years ago

3 0

Answer:

See the answer below

Explanation:

The complete question can be seen in the attached image.

Phenolphthalein is an indicator that is often utilized in an acid-base reaction to indicate the endpoints of such reactions due to its ability to change color from pink/colorless to colorless/pink depending on if the final solution is acidic or basic.

Phenolphthalein is usually colorless in acidic solutions and appears pink in basic solutions. The more basic or alkaline a solution is, the stronger the pink color of phenolphthalein. Hence;

1. Ammonia with a pH of 11 is basic, phenolphthalein will turn pink.

2. Battery acid with a pH of 1 is acidic, it will remain colorless.

3. Lime juice with a pH of 2 is acidic, it will remain colorless.

4. Mashed avocado with a pH of 6.5 is acidic, it will remain colorless.

5. Seawater with a pH of 8.5 is basic, it will turn pink.

6. Tap water with a pH of 7 is neutral, it will remain colorless

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When we can get Pka for K2HPO4 =6.86 so we can determine the Ka :

when Pka = - ㏒ Ka

6.86 = -㏒ Ka

∴Ka = 1.38 x 10^-7

by using ICE table:

H2PO4- → H+ + HPO4
initial 0.4 m 0 0

change -X +X +X

Equ (0.4-X) X X

when Ka = [H+][HPO4] / [H2PO4-]

by substitution:

1.38 X 10^-7 = X^2 / (0.4-X) by solving for X

∴X = 2.3x 10^-4

∴[H+] = X = 2.3 x 10^-4

∴PH = -㏒[H+]

= -㏒ (2.3 x 10^-4)
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2 years ago

25 g of ethyl alcohol is dissolved in 100 ml of water (density = 0.99993 at 20 oc). what is the % w/w for the ethyl alcohol in t

vitfil [10]

Percentage by mass is the amount in mass of a component in a mixture per 100 unit of mass of the total mixture. Percentage by mass is the same as %w/w. We can determine this by dividing the mass of the solute with the total mass of the mixture. However, from the problem statement, we are given the volume of the water so there is a need to convert this value to mass by using the density of water. We calculate as follows:

Mass of solution = 100 mL (0.99993 g/mL) water + 25 g EtOH
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2 years ago

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