Kevlar is the high-strength polymer material. it has the following composition: 70.58% carbon, 11.76% nitrogen, 4.23% hydrogen, and 13.43% oxygen. calculate the empirical formula for kevlar.(enter the elements in the order: c, h, n, o.)

Answer : The empirical formula for kevlar is,

Solution : Given,

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

Mass of C = 70.58 g

Mass of H = 4.23 g

Mass of N = 11.76 g

Mass of O = 13.43 g

Molar mass of C = 12 g/mole

Molar mass of H = 1 g/mole

Molar mass of N = 14 g/mole

Molar mass of O = 16 g/mole

Step 1 : convert given masses into moles.

Moles of C =

Moles of H =

Moles of N =

Moles of O =

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For C =

For H =

For N =

For O =

The ratio of C : H : N : O = 7 : 5 : 1 : 1

The mole ratio of the element is represented by subscripts in empirical formula.

The Empirical formula =  =

Therefore, the empirical formula for kevlar is,

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

he would use the colour black