A compound is known to have an empirical formula of CH and a molar mass of 78.11 g/mol.  What is its molecular formula?

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enotechris's profile pic

enotechris | College Teacher | (Level 2) Senior Educator

Posted on

The molar mass of Carbon (C) is 12.01 g/mol, and the molar mass of Hydrogen (H) is 1.00 g/mol. Adding these togther gives us the molar mass of the empirical formula:

molar mass CH = (12.01 g/mol) + (1.00 g/mol) = 13.01 g/mol

We know that molar mass of the given compound to be 78.11 g/mol; dviding that by the molar mass of the empirical formula gives us a mole ratio:

mole ratio CH = (78.11 g/mol) / (13.01 g/mol) = 6

So for 6 moles of carbon we have 6 moles of hydrogen, or

C6H6, otherwise known as Benzene.

Sources:
maria-vivanco's profile pic

maria-vivanco | Student, Grade 11 | (Level 1) Valedictorian

Posted on

Empericalformula of CH and a molar mass of 78.11 

To find the molecular formula: 

1. Find the molar mass of EF:

CH: 

Carbon: 1x12= 12

Hydrogen= 1x1= 1 

Molar mass 13

2. Write the molar mass of the actual compound given: 

78.11

3. Make a proportion of the molar mass: ` `

`(MFM)/(EFM)` = `(78.11)/(13)`` `

`cong` 6

4. Multiply the number to the emperical formula 

C(6)H(6)= 

C6H6

` `

Jyotsana's profile pic

Jyotsana | Student, Grade 10 | (Level 1) Valedictorian

Posted on

CH= 12+1=13g/mole

MFM/EFM= 78.11/13= 6

Molecular Formula= C6H6

Yojana_Thapa's profile pic

Yojana_Thapa | Student, Grade 10 | (Level 1) Valedictorian

Posted on

Molar Mass / Empirical Formula mass = the factor!

Molar Mass = 78.11 g/moL

Empirical Formula mass = ?

  • CH = (12.01) + (1.00 ) = 13.01 g/mol

So...

(78.11 g/moL) / (13.01g/moL EF mass) = 6 

'6' is the factor

(CH)6 = C6H6

Molecular Formula = C6H6

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