When magnesium ion doesn't give any characteristics colour with the flame test as electronic transisitons do not give out visible light.
The elements in the periodice table are not listed in alphabetical order, because the arragement in rows (periods) and columns (groups or familes), in increasing order of atomic number (number of protons of the atoms) permits to explain similarities among the elements, trend in some properties, and even predict properties of unknown elements.
For example, the elements of the first group (family), called alkaline metals, all have 1 valence electron, have similar physical properties (ductibility, malleability, luster, thermal and electricity conductivity), react in similar way with water, show a trend in the atomic radii and in the ionization energy.
You can tell similar stories for other groups like, alkalyne earth metals, halogens and noble gases.
You can also tell trends in electroneativities, and atomic radii, for a row of elements, as per the order they are in the row.
So, the current array resulted very helpul for chemists to explain and predict the behavior and properties of the elements.
The reaction that has the greatest tendency to be reversed in an spontaneous redox reaction is that whose forward standard reduction potential is the lowest (mos negative) one because that means that the reversed reaction will have the highest (most positive) standard reduction potential.
So, the answer is Cr(3+) + 3e- ---> Cr(s) with Eo = -0.91 V, whose reversed reaction is Cr(s) - 3e- ---> Cr (3+) with Eo = +0.91 V.
Answer: the second option Cr(3+) + 3e- ---> Cr(s) Eo = -0.91 V
The reaction of acetic acid with sodium hydroxide is:
The ratio of A-/HA is calculated as follows:
According to Henderson Hasslebach equation:
![[A-]/[HA] = 10^p^H^-^p^K^_a](https://tex.z-dn.net/?f=%5BA-%5D%2F%5BHA%5D%20%3D%2010%5Ep%5EH%5E-%5Ep%5EK%5E_a)
The total concentration of HA and A- = 2.0 L * 0.25 M = 0.5 mol.
![[ A- ]+ [ HA ]= 0.5](https://tex.z-dn.net/?f=%5B%20A-%20%5D%2B%20%5B%20HA%20%5D%3D%200.5)
![[ A^- ] = 0.5 – [ HA]](https://tex.z-dn.net/?f=%5B%20A%5E-%20%5D%20%3D%200.5%20%E2%80%93%20%5B%20HA%5D)
[ HA] = 0.156 mol and [ A- ]= 0.343 mol
Total of 0.5 moles of acetic acid is required:
HA = 30.0 g acetic acid
Conversion of 0.343 moles of the acetic acid to acetate can be performed by adding NaOH
= 343 mL
Thus, 343 mL of 1M NaOH is required
