Math and Arithmetic

# How do you calculate the molecular formula of a substance which contain 80 percent C and 20 percent H?

###### Wiki User

You can only calculate the empirical formula because you do not have a mass of this compound given. To do the empirical formula assume 100 grams and change percent to grams. Get moles.

80 grams Carbon (1 mole C/12.01 grams) = 6.66 moles C

20 grams hydrogen (1 mole H/1.008 grams) = 19.84 moles H

the smallest becomes 1 in the empirical formula and the other number is divided by it, Thus; H/C

19.84 moles H/6.66 moles C

= 2.9, which we call 3

so,

CH3

---------------

is the empirical formula

To get the molecular formula tour question needed to read; How to calculate molecular formula from such ans such mass of compound with these percentages of elements, Which, of course, your question did not provide.

Then you would have divided that given mass by the mass total of the elements of the empirical formula, got a whole number by which you would have multiplied the numbers of your empirical formula to get molecular formula.

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## Related Questions

### What does compounds molecular formula tells what?

Molecular formula of a chemical substance is representative for the composition of this chemical substance.

### What is the molecular formula of a substance that has an empirical formula of C2H5 and a molecular mass of 58 grams per mole?

The molecular formula of a substance that has an empirical formula of C2H5 and a molecular mass of 58 grams per mole is C4H10 Butane.

### Can you determine the molecular formula of a substance from its percent composition?

Not completely. The empirical formula of a substance can be determined from its percent composition, but a determination of molecular weight is needed to decide which multiple of the empirical formula represents the molecular formula.

### How is a molecular formula determined?

The molecular formula is the number and type of atoms that are present in a single molecule of a substance.

### How to calculate empirial formula from molecular formula?

the empirical formula would just be the smallest whole number ratio from the molecular formula

### Explain why the percent composition of certain compounds are not sufficient to determine the compounds molecular formulas?

Because unlike the empirical formula, the molecular formula does not have to be the simplest ratio.If by chance you are given the percent composition of the elements in a substance, you could calculate the empirical formula and then the empirical formula's mass. However, the molecular formula equation is molecular formula= (empirical formula)n, where n is the mass of the molecular formula divided by the mass of the empirical formula. You would, therefore, need to know the mass belonging to the molecular formula, which you are not given.

### It is possible to determine the molecular formula of a substance from its percentage composition?

From the percentage composition only, an empirical formula can be derived, but a proper molecular formula can only be assured by adding some information about the molecular weight of the substance concerned.

### Define emperical formula and molecular formula?

Molecular formula is the actual representation of the constitution of the substancewhile Empirical formula is the simplest representation of the molecular formula.Molecular formula= Empirical formula*n(where n= Molecular weight/Empirical formula weight)Example :-EtheneMolecular formula =C2H4Empirical formula=CH2here CH2 is the simplest representation of molecular formula of Ethene.

### Which formula represents a molecular compound?

A molecular formula contain indication about the chemical composition of the compound but no information about the structure.

### How to calculate Molecular formula from empirical formula?

If you know the molar mass of the compound, you have to calculate the mass of the empirical formula and divide the molar mass of the compound by the mass of the empirical formula in order to find the ratio between the molecular formula and the empirical formula. Then multiply all the atoms by this ratio to find the molecular formula!

### Describe the differences between molecular formulas and structural formulas for molecular compounds?

A molecular formula is a brutto formula.The structural formula contain also a description of the geometry of the compound.

### Does sugar contain gluten?

Pure table sugar has the chemical name of sucrose, with the molecular formula of C12H22O11. Glutens are a separate substance altogether in comparison.

### What other information is required to know whether a formula is both empirical and molecular?

Find the mass of the substance and divide it by the mass of the substance defined by the empirical formula. If you get 1, then the empirical formula is also the molecular one.

### What substances have NaC18H35O2?

That is a fictitious molecular formula; no substance contains it.

### What is the identity of a substance?

The identity of a substance (chemical compound) is defined by his chemical formula and molecular structure.

### If the compounds contain the same formula will they also contain the same molecular formula?

No? Consider starch and cellulose; same formula extremely different properties.

### What is the molecular formula of silver?

Ag is the molecular formula for silver. If you look on a periodic table, you will find this substance with the transitional metals and with the atomic number of 47.

### What does sulphuric acid contain?

sulphur and hydrogen the molecular formula is H2SO4

### Why is sugar a pure substance?

Sugar is a pure substance because it has a definite composition. Its molecular formula is C12H22O11.

### How do you determine the molecular formula given the empirical formula?

Calculate the empirical formula weight. Find the ratio of the molecular weight to the empirical formula weight. (n= molecular weight/ empirical formular weight). Multiply each subscript of the empirical formula by n.

### How do you calculate Molecular formula from empirical formulaWhat could you do with that information to determine that the empirical and molecular formulas are related to one another by a factor of 6?

In order to find molecular formula from empirical formula, one needs to know the molar mass of the molecular formula. Then you simply divide the molar mass of the molecular formula by the molar mass of the empirical formula to find out how many empirical formulae are in the molecular formula. Then you multiply the subscripts in the empirical formula by that number.