What is the molecular formula of the compound with a molecular weight of 112 g/mol and percent composition: 85.6% C and 14.4% H? Select one:
a. C2H4
b. CH2
c. C4H8
d. C8H16

Molecular formula = C₈H₁₆

Explanation:

Given data:

Percentage of hydrogen = 14.4%

Percentage of carbon = 85.6%

Molecular formula = ?

Molecular weight = 112 g/mol

Solution:

Number of gram atoms of H = 14.4/ 1.01 = 14.26

Number of gram atoms of C = 85.6/ 12 = 7.13

Atomic ratio:

            C                      :              H        

           7.13/7.13            :           14.26/7.13    

            1                      :                 2          

C : H = 1 : 2

Empirical formula is CH₂

Molecular formula:

Molecular formula = n (empirical formula)

n = molar mass of compound / empirical formula mass

n = 112 / 14

n = 8

Molecular formula = n (empirical formula)

Molecular formula = 8 (CH₂)

Molecular formula = C₈H₁₆

answer : the correct answer is 2) hno₃ and naoh .

arrhenius concept of acid and base :

acid :

according to arrhenius acid are those which release h⁺ or hydronium ion (h₃o⁺) in aqueous solution .

example : hcl +h₂o ↔ h₃o⁺ + cl⁻

hcl is giving h₃o⁺ ion in water , hence it is an arrhenius acid .

base :

according to arrhenius , bases are those which releases oh⁻ ions in aqueous solution .

example : koh (aq) ↔ k⁺ + oh⁻

since koh is producing oh⁻ ions hence , it is an arrhenius base .

checking the options :

1) ch₃oh and naoh :

ch₃oh is known as methanol , an organic compound , which is neutral compound . the dissociation of ch₃oh is negligible . it is very very weak acid (ka = 3.2 * 10 ⁻¹² ) .

naoh being ionic gives na⁺ and oh⁻ ions in aqueous solution as :

naoh ↔ na⁺ + oh⁻ . hence it is an arrhenius base

it can be concluded that ch₃oh and naoh is not arrhenius acid and base.

2) hno₃ and naoh :

hno₃ is an ionic compound which gives ions h⁺ and no₃⁻ ion in aqueous solution as:

hno₃ + h₂o ↔ h₃o⁺ + no₃⁻

since it is giving h⁺ ion . hno₃ is arrhenius acid .

naoh being ionic gives na⁺ and oh⁻ ions in aqueous solution as :

naoh ↔ na⁺ + oh⁻

. hence it is an arrhenius base .

it can be said that hno₃ and naoh are arrhenius acid and base.

3) ch₃oh and hcl

as discussed ch₃oh is neutral compound .

while hcl in aqueous solution dissociates to give h⁺ and cl⁻ ions as :

hcl + h₂o→ h₃o⁺ + cl⁻ . so hcl is arrhenius acid .

hence , ch₃oh and hcl are not arrhenius acid and base.

4) hno₃ and hcl :

hno₃ as discussed gives h⁺ in aqueous solution , while hcl also gives h⁺ in aqueous solution .

hence both hno₃ and hcl are arrhenius acid they are not acid and base .

so the arrhenius acid and base are 2) hno₃ and naoh.