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A buffer is composed of a weak acid and its conjugate base or a weak base and its conjugate acid. From the given list:
HCl and HF: Strong Acid and Weak Acid. NOT BUFFER
HF and NaF: Weak Acid and Conjugate Base. BUFFER
HC₂H₃O₂ and KC₂H₃O₂: Weak Acid and Conjugate Base. BUFFER
NaOH and NH₃: Strong Base and Weak Base. NOT BUFFER.
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<u>Answer:</u> The quantity relating pressure and volume is 
and the size of the tank must be 
<u>Explanation:</u>
To calculate the new volume, we use the equation given by Boyle's law. This law states that pressure is inversely proportional to the volume of the gas at constant temperature.
Mathematically,
Or,
The equation given by this law is:
where,
are initial pressure and volume.
are final pressure and volume.
We are given:
Putting values in above equation, we get:
Hence, the size of the tank must be
<h3>Answer:</h3>
Br (Bromine)
<h3>Explanation:</h3>
Li and K,
As the electronegativity difference between Li and K is less than 1.7 therefore, ionic bond cannot form between these two metals.
Li and Fe,
The electronegativity difference is less than 1.7 so neither electron loss nor electron gaining will take place between these two metals. Therefore, there will be no ionic bond between them.
Li and Kr,
As Krypton is a noble gas and does not react due to complete octet hence the formation of KrLi is difficult. However, Krypton can make compounds like KrF₂ e.t.c. Therefore we can skip this option.
For Li and K,
E.N of Bromine = 2.96
E.N of Lithium = 0.98
________
E.N Difference 1.98 (Ionic)
This ionic compound is possible and is the correct option because ionic compounds are always made by metals and non metals and here the combination is perfect.
<h3>Conclusion:</h3>
Lithium (a metal) and form Ionic bond with Bromine (a non metal)
