Answer:
1.58x10⁻⁵
2.51x10⁻⁸
0.0126
63.10
Explanation:
Phenolphthalein acts like a weak acid, so in aqueous solution, it has an acid form HIn, and the conjugate base In-, and the pH of it can be calculated by the Handerson-Halsebach equation:
pH = pKa + log[In-]/[HIn]
pKa = -logKa, and Ka is the equilibrium constant of the dissociation of the acid. [X] is the concentrantion of X. Thus,
i) pH = 4.9
4.9 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = - 4.8
[In-]/[HIn] = 
[In-]/[HIn] = 1.58x10⁻⁵
ii) pH = 2.1
2.1 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = -7.6
[In-]/[HIn] = 
[In-]/[HIn] = 2.51x10⁻⁸
iii) pH = 7.8
7.8 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = -1.9
[In-]/[HIn] = 
[In-]/[HIn] = 0.0126
iv) pH = 11.5
11.5 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = 1.8
[In-]/[HIn] = 
[In-]/[HIn] = 63.10
Answer: helium(He)
Explanation: Helium has only 2 electrons in the outermost energy level, but all of the other elements in its column have eight.
Some possible public policies aimed at reducing the amount of carbon dioxide in the air is that companies should make use of new emissions technology to avoid air pollution.
<h3>
What is air pollution?</h3>
What is air pollution?Air pollution is the release of substance that are dangerous or harmful to human health into the environment.
Excessive release of carbon dioxide into the atmosphere causes pollution and deplete our ozone layer.
One of the policy government have out in check is that all companies should purchase or make use of new emissions technology to avoid polluting the environment and causing harm to human health.
Therefore, some possible public policies aimed at reducing the amount of carbon dioxide in the air is that companies should make use of new emissions technology to avoid air pollution.
Learn more on air pollution here,
brainly.com/question/10004402
solution:
Physical properties describe how a material looks. such as color, state of matter, shininess, Other physical properties include density, mp, bp, brittleness, malleability, conductivity, ductility, solubility in water. A physical property can be determined without changing the identity of the material.
Chemical properties describe how a material behaves.such as does it burn, does it corrode, does it react with air, does it react with water, does it act like a metal by giving away electrons o like a nonmetal by taking electrons, what type of bonds will it form, or is it inert, is it acidic or basic, Chemical properties can only be determined during a chemical reaction.
