P ic of question? it will. help
Answer:
Explanation:
The best choice to prepare a buffer of pH 9.0 is a conjugate acid/base pair in which the acid has pKₐ = 9.0 ± 1.
Let's examine each of the choices.
A. NH₃/NH₄Cl
For NH₃, = pK_b = 4.75
For NH₄⁺, pKₐ 14.00 - 4.75 = 9.25
B. HCHO₂/NaCHO₂
For HCHO₂, pKₐ = 3.74
C. C₅H₅N/ C₅H₅NHCl
For C₅H₅N, = pK_b = 8.76
For C₅H₅N⁺, pKₐ 14.00 – 8.76 = 5.21
D. HNO₂/NaNO₂
For HNO₂, pKₐ = 3.33
The only acid with a pKₐ close to 9.0 is the ammonium ion.
The best buffer to prepare a buffer with pH 9.0 is
Answer:
Density = mass/volume
= 44/22.4
= 1.96 gram/liter
The density of the Carbon Dioxide at S.T.P. (Standard Temperature and Volume) is 1.96 gram/liter.
1. Curiosity
2.<span> Necessity</span>
Answer:
The respective figure with label and targets is missing but yet the definitions and stability considerations can help you, so I explain them below.
Explanation:
Remember these definitions:
- Atomic number = number of protons
- Mass number = number of protons + number of neutrons
Hence,
- When one proton is added, both atomic number and mass number increase by one.
- When one neutron is added, atomic number remains the same, but mass number increase.
The neutrons provide stability to the nucleus of the atom by compensating the electrostatic repulsion force that arise from the fact that positive charges are forced to be so close in the nucleus.
Since the more protons are added to the nucleus the stronger the repulsive force inside the nucleus are, as the atomic number increase the neutron number must increase too.
For the ligther elements (lower atomic and mass numbers) the ratio of neutrons to protons is very close to 1.
For heavier elements (greater atomic and mass numbers) the ratio of neutrons to protons increase: proportionally more neutrons are needed to provide stability to the nucleus.