Answer:
The temperature will be 137 K for the gas pressure to remain constant
Explanation:
If the gas pressure keeps on constant, volume of the gas will be modified according to temperature.
V1 / T1 = V2 / T2
4L / 274K = 2L / T2
(4L / 274K) . T2 = 2L
T2 = 2L . (274K / 4L)
T2 = 137K
It is natural and u can't by it
Acids are chemicals with a pH less than 7 that can donate a proton or H+ ion in a reaction. Bases have a pH greater than 7 and can accept a proton or produce an OH- ion in a reaction. If you mix equal amounts of a strong acid and a strong base, the two chemicals essentially cancel each other out and produce a salt and water. Mixing equal amounts of a strong acid with a strong base also produces a neutral pH (pH = 7) solution. This is called a neauturization and looks like
HA + BOH → BA + H2O + heat
Answer: The salt which has the highest pH is 
Explanation: Salts are formed by the reaction of acid and base. General equation for the generation of salt is given by:

The given salts are formed from the reaction of acids and bases.
1) 
This is a salt formed by the reaction of strong base (KOH) and strong acid
. So, this salt is a neutral salt.

2) 
This is a salt which is formed by the reaction of weak base
and strong acid
. So, this salt is an acidic salt.

3) 
This is a salt which is formed by the reaction of weak base
and strong acid (HCl). So, this salt is an acidic salt.

4) 
This is a salt which is formed by the reaction of strong base (NaOH) and weak acid
. So, this salt is a basic salt.

Now, we have to find the salt which has the highest pH value.
Highest pH value means that the salt must be basic in nature and from the given salts, only
is basic salt. Hence, this salt has the highest pH value.