Answer: Option (4) is the correct answer.
Explanation:
It is known that equilibrium constant is represented as follows for any general reaction.

K = ![\frac{[C][D]}{[A][B]}](https://tex.z-dn.net/?f=%5Cfrac%7B%5BC%5D%5BD%5D%7D%7B%5BA%5D%5BB%5D%7D)
As equilibrium constant is directly proportional to the concentration of products so more is the value of equilibrium constant more will be the number of products formed.
As a result, more is the time taken by the reaction to reach towards equilibrium. Whereas smaller is the value of equilibrium constant more rapidly it will reach towards the equilibrium.
Thus, we can conclude that cases where K is a very small number will require the LEAST time to arrive at equilibrium.
1: if the solid is heating and is not yet to the melting point, the answer would be "solid". If the substance reached the melting point and is heating up at that point, the answer would be "solid and liquid" (yes, at the same time).
2. boiling point.
Once the substance is melted completely into a liquid, the highest point where the substance will still exist as a liquid would be the boiling point.
3. gas.
The three main states of matter from cooler to hotter are:
solid, liquid, and gas.
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