Mass 6.00 g of a certain compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 180. g/mol, is burned
completely in excess oxygen, and the mass of the products carefully measured:
product
carbon dioxide 8.80 g
3.60 g
Use this information to find the molecular formula of X.
water
alo
O
х
?

The molecular formula =C₆H₁₂O₆

Given

6.00 g of a certain compound X

The molecular molar mass of 180. g/mol

CO₂=8.8 g

H₂O=3.6 g

Required

The molecular formula

Solution

mass C in CO₂ :

= 1.12/44 x 8.8

= 2.4 g

mass H in H₂O :

= 2.1/18 x 3.6

= 0.4 g

Mass O in compound :

= 6-(2.4+0.4)

= 3.2 g

Mol ratio C : H : O

= 2.4/12 : 0.4/1 : 3.2/16

= 0.2 : 0.4 : 0.2

= 1 : 2 : 1

The empirical formula : CH₂O

(CH₂O)n=180 g/mol

(12+2+16)n=180

(30)n=180

n=6

(CH₂O)₆=C₆H₁₂O₆

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.