D is a scintillation counter.
Answer:
B..........................
NH₃ + H₂O ⇄ NH₄⁺ + OH⁻
pOH=-lg[OH⁻]
pOH = 14-pH
14-pH = -lg[OH⁻]
[OH⁻]=10^(pH-14)
[OH⁻]=10^(11.8-14)=0.00631 = 6.31·10⁻³ mol/L
covalent bonds can form between two nonmetal atoms
covalent bonds can form between atoms of the same element
covalent bonds can form between atoms of different elements