Terephthalic acid used in the production of polyester fibers and films is composed of carbon, hydrogen, and oxygen. when 0.6943 h og acid is subjected to combustion analysis it produced 1.471 g co2 and 0.391 g h20. what is its empirical and molecular formula if its molar mass is 172 g/mol

Empirical formula: C₂H₃O

Molecular formula: C₈H₁₂O₄

Explanation:

After the reaction, all the carbon will form CO₂ and all the hydrogen will form H₂O, so the number of moles of each element will be the same as in the terephthalic acid. Knowing the molar masses: C = 12 g/mol, H = 1 g/mol, and O = 16 g/mol. CO₂ = 12 + 2x16 = 44 g/mol, H₂O = 2x1 + 16 = 18 g/mol.

The number of the moles of the compounds are the mass divided by the molar mass so:

CO₂ = 1.471/44 = 0.0334 mol

H₂O = 0.391/18 = 0.0217 mol

There is 1 mol of C in each mol of CO₂, so there is 0.0334 mol of C.

There are 2 mol of H in each mol of H₂O, so there is 0.0434 mol of H.

Which are the same of in the acid. The masses of the compounds are:

mC = 0.0334x12 = 0.400 g

mH = 0.0434x1 = 0.0434 g

mO = 0.6943 - (0.4 + 0.0434) = 0.2509 g

The number of moles of O is: 0.2509/16 = 0.0157 mol

To know the empirical formula, let's divide the number of moles of the elements for the samllest: 0.0157 mol

C = 0.0334/0.0157 = 2

H = 0.0434/0.0157 = 3

O = 0.0157/0.0157 = 1

The empirical formula is C₂H₃O

The molecular formula will be the empirical multiplied by a factor (n):

n(C₂H₃O), so the molar mass will be: nx(2x12 + 3x1 + 16) = 172

43n = 172

n = 4

So the molecular formula is 4x(C₂H₃O) = C₈H₁₂O₄.

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.