Answer:
d. 97.60 g
Explanation:
Given parameters:
Number of moles of formaldehyde = 3.25moles
Ratio:
C H O
1 2 1
Unknown:
Mass of this sample = ?
Solution:
The empirical formula of a compound is its simplest formula. It is the simplest whole number ratio of the atoms in a given substance.
The molecular formula is the actual formula of the compound.
Since the molecular and empirical formula are the same here, the formula of the compound is;
CH₂O
To find the mass of the formaldehyde, use the expression below;
Mass = number of moles x molar mass
molar mass of CH₂O = 12 + 2(1) + 16 = 30g/mol
Mass = 3.25 x 30 = 97.5g
Explanation :
As we know that Mendeleev arranged the elements in horizontal rows and vertical columns of a table in order of their increasing relative atomic weights.
He placed the elements with similar nature in the same group.
According to the question, the atomic weight of iodine is less than the atomic weight of tellurium. So according to this, iodine should be placed before tellurium in Mendeleev's tables. But Mendeleev placed iodine after tellurium in his original periodic table.
However, iodine has similar chemical properties to chlorine and bromine. So, in order to make iodine queue up with chlorine and bromine in his periodic table, Mendeleev exchanged the positions of iodine and tellurium.
As we know that the positions of iodine and tellurium were reversed in Mendeleev's table because iodine has one naturally occurring isotope that is iodine-127 and tellurium isotopes are tellurium-128 and tellurium-130.
Due to high relative abundance of tellurium isotopes gives tellurium the greater relative atomic mass.
Answer:
In a semiconductor, the bonding molecular orbitals that contain electrons are referred to as the valence band, while the antibonding orbitals that are completely empty are referred to as the conduction band.
The conduction band occupies a higher energy level than the valence band. The band gap is what separates the two orbitals.
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