Imagine you are given a mystery element. It is, however, a discovered and known element. You may perform a maximum of two observ
ations or tests to determine its identity. Time and money is critical, so you need to prioritize your tests. If you can identify the mystery element with a single test, you get 100 super-geek points from your research lab team.
Pick two tests and justify why you think they will identify the mystery element with certainty. If you think the first test will be enough, explain why.
Choose from these available tests:
• classification into metal, nonmetal, or metalloid
• count of valence electrons
• count of electron shells
• atomic radius (error range: +/- 1 pm)
• electronegativity (error range: +/- 0.1)
• first ionization energy (error range: +/- 10 kJ/mole)
• melting point (error range: +/- 10 C)
• boiling point (error range: +/- 20 C)
Pick two tests and justify why you think they will identify the mystery element with certainty. If you think the first test will be enough, explain why.
Choose from these available tests:
• classification into metal, nonmetal, or metalloid
• count of valence electrons
• count of electron shells
• atomic radius (error range: +/- 1 pm)
• electronegativity (error range: +/- 0.1)
• first ionization energy (error range: +/- 10 kJ/mole)
• melting point (error range: +/- 10 C)
• boiling point (error range: +/- 20 C)
2 answers:
Answer:
Count of Valence electron followed by electron shells
Explanation:
The periodic table has certain very unique properties that help identify the elements.
The number of valence electrons in any element can be determined by the placement of the element in the group. An element from group III will have three valence electrons.
Hence, this test will help locate the group of the element in question.
This test should be followed by the number of electron shells.
In the Periodic table, the placement of any element in the row depends on the number of electron shells. An element from row II will have two electron shell.
These two tests will work like coordinates on the Periodic Table.
For example, the result is Group II, Row 3 is Calcium.
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Answer:
(a) 45.17×10^-14 kg/s
(b) since the amount of helium escaped due to diffusion is insignificant, the final pressure drop in the tank remains the same as the initial pressure 500kPa.
Explanation:
Helium gas at temperature T=293k
Helium gas at pressure P= 500kPa
The inner diameter of spherical tank is
The inner radius of spherical tank is :
=
=1m
Thickness of the container r = 1cm =0.01m
Outer radius of the spherical tank is ;
t =
multiplying through with (-) we have ;
From table of binary diffusion coefficients of solids, the diffusion coefficients of helium in silica is noted as
From table molar mass and gas constant, the molecular weight of helium is:
M = 4.003kg/kmol
The solubility of helium in fused silica is determined from Table of Solubility of selected gases and soilids.
= 0.00045 kmol/m³. bar
Considering total molar concentration as constant, the molar concentration of helium inside the container is determined as
= 0.00045kmol/m³. bar × (5)
From one dimensional mass transfer through spherical layers is expressed as:
substituting all the values in the above relation, we have;
(a) The mass flow rate is expressed as
(b) The pressure drop in the tank after a week;
For one week the mass flow rate of helium is
The volume of the spherical tank is
V = 4.189m³
The initial mass of helium in the sphere is determined from the ideal gas equation:
PV=NRT
where R is the universal gas constant and its value is R = 8.314 KJ/Kmol.k
N= PV/RT
N= 500 × 4.189/ 8.314 × 293
N= 0.86kmol
The number of moles of helium gas remaining in the tank after one week is:
therefore, since the amount of helium escaped due to diffusion is insignificant, the final pressure drop in the tank remains the same as the initial pressure 500kPa.