Potential energy would increase because you are compressing the spring
I am sure it is a.12150sn and 11950sn because isotopes are the same atoms but different number of protons
Surface tension. Im not sure if this is completely right but I hope I helped :)
pH=2.7
<h3>Further explanation</h3>
Acetic acid = weak acid
![\tt [H^+]=\sqrt{Ka.M}](https://tex.z-dn.net/?f=%5Ctt%20%5BH%5E%2B%5D%3D%5Csqrt%7BKa.M%7D)
Ka = acid ionization constant
M = molarity
Ka for Acetic acid(CH₃COOH) : 1.8 x 10⁻⁵
![\tt [H^+]=\sqrt{1.8\times 10^{-5}\times 0.222}\\\\=0.001998=1.998\times 10^{-3}](https://tex.z-dn.net/?f=%5Ctt%20%5BH%5E%2B%5D%3D%5Csqrt%7B1.8%5Ctimes%2010%5E%7B-5%7D%5Ctimes%200.222%7D%5C%5C%5C%5C%3D0.001998%3D1.998%5Ctimes%2010%5E%7B-3%7D)

25 kj absorbed by dissolving 1 mole of NH4NO3
1kj is absorbed by dissolving = 1/25.7 = 0.03891 moles
what about 73 kj absorbed by dissolving
0.03891 x73= 2.8404 moles