How to find the molecular formula out of the molar mass?

  • Context: Chemistry 
  • Thread starter Thread starter jessicah211
  • Start date Start date
  • Tags Tags
    Formula Mass Molecular
Click For Summary
SUMMARY

The discussion focuses on determining the molecular formula from a given molar mass, specifically using the example of an industrial solvent with a molar mass of 78.0 g and an empirical formula of CH. The process involves calculating the mass of the hypothetical group (C1H1), which totals 13 g, and determining how many such groups fit into the molar mass of 78.0 g, resulting in the molecular formula C6H6, identified as Benzene. Additionally, the discussion addresses calculating the number of moles in 35 g of potassium chloride (KCl) by using its molar mass of 74.6 g, yielding approximately 0.47 moles.

PREREQUISITES
  • Understanding of empirical and molecular formulas
  • Basic knowledge of molar mass calculations
  • Familiarity with the periodic table
  • Concept of moles in chemistry
NEXT STEPS
  • Study the calculation of empirical formulas from molar mass
  • Learn about molar mass determination for various compounds
  • Explore the concept of moles and Avogadro's number in detail
  • Investigate the properties and applications of Benzene in industrial chemistry
USEFUL FOR

Chemistry students, educators, and professionals involved in chemical analysis and molecular structure determination will benefit from this discussion.

jessicah211
Messages
1
Reaction score
0
Here is the problem. I have a series of questions that I don't know how to do. They are all basically the same so I will just give an example of one and if I could get a point the right direction that would be great!

The molar mass of an important industrial solvent is 78.0 g and its empirical formula is CH. What is its molecular formula?

Anther slightly related question that might be answered as part of the first question is

How many moles are in 35 g of potassium chloride?
 
Physics news on Phys.org
What is molar mass of the hypothetic CH group? How many such groups are needed for the molecule to have molar mass of 78?
 
As Borek said,

(CxHy)n = 78.0 (You are given 1 x and 1 y)

1) Find the mass of the hypothetical group
here : x (mass of carbon = 12) + y (mass of hydrogen = 1) = 13

2) Find how many possible hypothetical groups you can have for 78.0 g
here : n = 78.0 / 13.0 = 6,

3) Just multiply replace x,y and n and you will get the actual formula
here : (C1H1)6 = C6H6

... and you found Benzene :)

The second part is as simple. Just use a periodic table to find the mass of K and Cl, thus finding the mass of 1 mole of KCl, then just divide the mass given in the question:

1 mole = (35.5 + 39.1) 74.6 g
35 g = ( 35 / 74.6 ) 0.47 moles
 

Similar threads

Chemistry Finding the Chemical Formula and Relative Molecular Mass
  • · Replies 13 ·
Replies
13
Views
4K
Chemistry Finding the molecular formula of an unknown hydrocarbon
  • · Replies 4 ·
Replies
4
Views
3K
Chemistry How can I find the molecular formula in this problem?
  • · Replies 10 ·
Replies
10
Views
3K
Chemistry Combustion Analysis- Empirical and molecular formula
  • · Replies 8 ·
Replies
8
Views
4K
Chemistry How to get molality without using a molecular formula?
  • · Replies 1 ·
Replies
1
Views
2K
Chemistry Find Empirical Formula of Unknown Substance
  • · Replies 5 ·
Replies
5
Views
2K
Chemistry Calculating the Mass of a Precipitate
  • · Replies 14 ·
Replies
14
Views
13K
Chemistry Molecular formula of organic compound
  • · Replies 2 ·
Replies
2
Views
2K
Chemistry How to understand the energy involved in mass transfer into an open system?
  • · Replies 0 ·
Replies
0
Views
2K
Chemistry Relation between molecular mass and molar mass
  • · Replies 4 ·
Replies
4
Views
24K